or  THE 
UNIVERSITY 

or 


Showing  Method  of  Determining  Elastic  Behavior  of  Concrete  Bars,  6x6-Inches  in  Cross- 
Section.  Specimen,  with  Electric  Extensometer  Attached,  Mounted  for  Compression  in 
the  150,000  Pound  Emery  Testing  Machine  of  Columbia  University. 


•CEMENTS, 
MORTARS  AND  CONCRETES 


THEIR  PHYSICAL  PROPERTIES 


MYRON  S.  FALK,  PH.  D., 

>  i 

INSTRUCTOR   IN   CIVIL  ENGINEERING  IN  COLUMBIA  UNIVERSITY 
IN  THE  CITY  OF   NEW  YORK. 


UNIVERSITY 

OF 


NEW  YORK 

M.    C.    CLARK 

1904 


GENERAL 

Copyright,  1904, 

BY 
MYRON   S,  FALK. 


INTRODUCTION. 

The  purpose  of  this  treatise  has  been  to  set  forth  as  concisely 
as  possible  the  physical  properties  of  cement  and  cement  mix- 
tures, with  principal  reference  to  those  properties  which  concern 
the  engineer.  The  results  of  investigations  made  upon  these  ma- 
terials have  been  examined  with  great  care.  Engineers  desiring 
such  data  on  cements,  mortars  and  concretes,  have  hitherto  been 
obliged  to  refer  to  numerous  scattered  articles  and  books.  It 
has  been  the  author's  object  to  abstract,  classify  and  summarize 
all  the  reliable  data  extant,  filling  in  certain  gaps  with  data  of  his 
own.  The  following  headings  outline,  for  the  greater  part,  the 
scope  of  the  work: 

General  Physical  Properties : 

Changes  in  Volume  When  Setting. 

Coefficient  of  Expansion  Due  to  Temperature  Changes. 

The  Action  of  Sea  Water  and  Salt. 

Porosity  and  Impermeability. 

Effect  of  Freezing. 

Adhesion  of  Iron  Rods  to  Cement  Mixtures. 

Fatigue  of  Cement  Mixtures. 

General  Elastic  Properties : 

Tensile  and  Compressive  Properties. 

Coefficient  of  Elasticity, 
Elastic  Limit. 
Ultimate  Resistance. 

Flexural  Properties. 

Coefficient  of  Elasticity. 
Modulus  of  Rupture. 

Shearing  Resistance. 

The  sources  from  which  the  experimental  data  have  been  ob- 
tained are  furnished,  in  every  instance,  with  those  data;  it  is 


1 26223 


iv  INTRODUCTION. 

therefore  unnecessary  to  give  separate  credit  to  the  various  ex- 
perimeriters  at/this  point.  It  is  proper  to  say,  however,  that  use 
has  beenrrratfe  only  of  those  results  which  gave  evidence  of  care- 
ful work,  so  that  no  conclusions  might  be  invalidated  by  reason 
of  the  unreliability  of  the  experiments.  Free  use  has  been  made 
of  the  Annual  Reports  of  the  Watertown,  Mass.,  Arsenal,  of  the 
Transactions  of  the  American  Society  of  Civil  Engineers,  and  of 
the  Proceedings  of  the  Institution  of  Civil  Engineers  of  Great 
Britain.  The  experiments,  not  previously  published,  made  under 
the  author's  direction  in  the  laboratories  of  Columbia  University, 
have  also  been  included. 

It  is  believed  that  the  results  obtained  relating  to  the  elastic 
properties  of  the  material,  such  as  the  values  of  the  coefficients 
of  elasticity  .and  the  ultimate  strengths,  have  been  so  analyzed 
that  these  values  may  be  determined  in  advance,  for  any  mix- 
ture, within  small  limits  of  error;  but  future  experiments  and 
future  improvement  in  the  manufacture  of  cement  mixtures  may 
cause  considerable  changes  in  these  figures. 

In  order  that  a  cement's  physical  peculiarities  may  be  more 
clearly  comprehended,  it  has  been  thought  advisable  to  consider 
as  a  preliminary  some  of  the  chemical  characteristics  of  cements. 
In  connection  with  the  discussion  of  chemical  compositions,  the 
theories  of  the  setting  of  cements  have  therefore  been  analyzed, 
and  it  has  been  possible  to  abstract,  in  an  appendix,  Mr;  Clif- 
ford Richardson's  theory  as  to  the  constitution  of  Portland 
cements.  In  addition,  a  chapter,  together  with  an  appendix, 
treating  briefly  of  the  ordinary  commercial  tests  has  been  in- 
cluded. M.  S.  F. 

August   22,    1904. 


CONTENTS. 


CHAPTER   I. 

CHEMICAL    PROPERTIES    OF   CEMENT. 

ART.                                                                                                                                                                 ^  PAGE 

1 .  Theories  of  Setting I 

2.  Chemical  Analyses 3 

Portland  Cements > 

Natural  Cements 6 

CHAPTER  II. 
PHYSICAL  TESTS  OF  CEMENT. 

3.  Commercial   Physical  Tests 9 

4-   Specific  Gravity  Tests   10 

5.  Fineness  Test II 

6.  Test  for  Time  of  Setting 13 

Action  of  Plaster  of  Paris 14 

Temperature  Affects  Time  of  Setting 16 

Retarding  the  Set 17 

Temperature  Changes  During  Setting 18 

7.  Tests  of  Tensile  Strength 19 

8.  Ratio  of  Compressive  and  Tensile  Strengths 26 

9.  Variations  in  the  Making  of  Tensile  Tests 29 

10.  Variations  of  Sands  in  Tensile  Tests 30 

Effect  of  Clay  in  Sand 34 

1 1.  Test  of  Constancy  of  Volume 39 

CHAPTER   III. 
GENERAL  PHYSICAL  PROPERTIES. 

12.  Variation  in  Volume  of  Cement  Mortars  in  Air  and  Water 40 

13-  The  Coefficient  of  Expansion  Due  to  Temperature  Changes    43 

14-  The  Action  of  Sea  Water  on  Cements 45 

Strength  in  Sea  Water 47 

Gauging  with  Salt  Water 50 

15-  Porosity  and  Permeability 51 

Feret' s  Conclusions 52 

16.  The  Effect  of  Freezing  on  Cement  Mixtures 55 

17.  Adhesion  of  Iron  in  Concrete 61 

18.  The  Fatigue  of  Cement  Mixtures 66 


vi  CONTENTS. 

CHAPTER  IV. 

ELASTIC  PROPERTIES  IN  GENERAL. 

19.  Treatment  of  Stress-Strain  Curves  ...............................        70 

CHAPTER  V. 
TENSILE  PROPERTIES. 

20.  Coefficient  of  Elasticity  and  Ultimate  Resistance  ..................        75 

Conclusions  .....................................  .............       97 

CHAPTER  VI. 
COMPRESSIVE   PROPERTIES. 

21.  Coefficient  of  Elasticity  and  Ultimate  Resistance  ..................        99 

22.  Ultimate  Compressive  Resistance  ................................      121 

Setting  Under  Water  ..........................................  130 

Wet  or  Dry  Concretes  ..........................................  130 

High  Temperatures  ............................................  132 

23.  Conclusions  ....................................................  132 

CHAPTER  VII. 
FLEXURAL  PROPERTIES. 

24.  The  Theory  of  Flexure  as  Applied  to  Concrete  ....................  142 

25.  Flexural  Coefficient  of  Elasticity  ................................  144 

26.  Modulus  of  Rupture  in  Bending  ..................................  149 

27.  Shearing  Resistance  and  Conclusion  .............................  157 

APPENDIX    I. 
Report  on  Uniform  Tests  of  Cement  by  the  .Special   Committee  of  the 

American  Society  of  Civil  Engineers  ...........................      159 

Sampling,  159;  Chemical  Analysis,  159;  Specific  Gravity,  160;  Fineness, 
161;  Normal  Consistency,  162;  Time  of  Setting,  163;  Standard  Sand, 
164;  Form  of  Briquette,  164;  Moulds,  164;  Mixing,  165;  Moulding, 
165;  Storage  of  the  Test  Pieces,  166;  Tensile  Strength,  166;  Constancy 
of  Volume,  1  67. 

APPENDIX    II. 
Constitution  of   Cement  ............................................      169 


Authors'  Index  .....................................................      175 


CHAPTER  I. 
CHEMICAL  PROPERTIES  OF  CEMENT. 

Definition — Cement  is  a  material  which  has  the  property  of  set- 
ting and  hardening  under  water,  and  is  composed  principally  of 
lime,  silica  and  alumina.  Two  forms  of  cement  are  commonly 
recognized,  natural  and  Portland,  and  to  these  the  following 
pages  will  be  entirely  restricted.  The  difference  between  these 
forms  is  principally  one  of  manufacture;  the  basic  principles  in 
both  varieties  are  the  same. 

Article  i — Theories  of  Setting. 

The  proper  chemical  constitution  of  cements  involves  the  con- 
sideration of  the  theory  of  the  setting  and  hardening  of  cements, 
the  reasoning  concerning  which  is,  at  the  present  time,  not  unani- 
mous. Chemists  have  not  definitely  determined  the  chemical 
changes  that  occur  when  water  is  added  to  dry  cement;  but  the 
conclusions  reached  by  Le  Chatelier  in  1887  and  by  the  New- 
berry  s  in  1897  have  been  accorded  more  weight  than  those  of 
others. 

Le  Chatelier'' s  Theory  ( Annales  des  Mines,  1887,  p.  345). 

Le  Chatelier  considers  that  when  the  raw  materials  of  a  cement 
have  been  burned  two  different  sets  of  compounds  possessing  the 
property  of  setting  and  hardening  upon  the  addition  of  water  may 
be  formed. 

In  the  first  case  he  considers  that  the  finished  material  contains 
lime  (CaO)  just  sufficient  in  amount  to  combine  with  the  silica 
(SiO2)  and  alumina  (A12OS)  to  form  tricalcic  silicate  (3CaO.SiO_>) 
and  tricalcic  aluminate  (3CaO.Al2O3).  These  compounds,  upon 
hydration,  set  and  harden.  He  finds  it  unnecessary  to  provide  lime 
to  react  on  the  sesquioxide  of  iron  which  may  be  present  in  the 


2  CHEMICAL  PROPERTIES  OF  CEMENT.  [Ch.  I. 

mixture,  since  the  calcic  ferrites  that  might  form  fall  to  powder 
upon  the  addition  of  water.  Magnesia  (MgO)  and  lime  he  con- 
siders as  possessing  equivalent  properties,  and,  therefore,  inter- 
changeable. In  this  case,  then,  no  multiple  silicates  of  alumina 
and  lime  are  formed;  and  in  order  that  the  finished  cement  may 
have  no  free  lime  existing  in  it,  Le  Chatelier  states  that  the  pro- 
portion of  lime  and  magnesia  to  silica  and  alumina  should  be 
subject  to  the  following  conditions: 

CaO+MgO  < 


The  objection  to  the  presence  of  free  lime  or  magnesia  is  due  to 
the  fact  that  they  blow  or  expand  in  volume  when  acted  upon  by 
water ;  disintegration  of  the  -cement  follows  and  it  becomes  unfit 
for  use. 

For  the  second  condition  Le  Chatelier  believes  that  only  tri- 
calcic aluminate  and  a  silico-aluminate  of  lime,  represented  by 
2SiO2.Al2O3.3CaO,  are  formed,  and  that  the  Fe2O3  acts  similarly 
to  A12O3  in  the  case  of  multiple  silicates  and  need  not  be  sepa- 
rated from  it. 

For  this  case  Le  Chatelier  states  the  condition  of  the  propor- 
tions of  the  constituents  as  follows: 

Ca  O+MgO         > 


The  Newberrys'  Theory  (J.  Soc.  Chem.  Ind.,  1897,  p.  889). 
The  conclusions  reached  by  Spencer  B.  and  W.  B.  Newberry 
are  quite  different;  it  is  their  belief  that  the  compounds  that 
harden,  upon  hydration,  are  tricalcic  silicate  and  dicalcic  alumi- 
nate, and  not  tricalcic  aluminate. 

Tricalcium  silicate  requires  2.8  parts  of  weight  of  lime  to  i  part 
of  silica,  and  dicalcic  aluminate  requires  i.i  parts  of  lime  to  I  of 
alumina.  The  Newberry  formula  for  a  theoretically  perfect  ce- 
ment is  therefore: 

2.8  Silica+i.i  Alumina 

Lime 

In  this  equation  the  materials  represent  percentages  of  weight 
in  the  cement. 


Art.  2.1  CHEMICAL  ANALYSES.  3 

The  Newberrys  also  conclude  that  Fe2O3  acts  similarly  to 
A12O3,  but  should  not  be  allowed  in  excess  of  5  per  cent.  In 
this  they  differ  from  Le  Chatelier.  Again,  Le  Chatelier's  for- 
mula places  magnesia  and  lime  of  equivalent  value  in  a  cement; 
the  Newberrys,  on  the  contrary,  consider  magnesia  inactive,  and 
to  perform  no  useful  function. 

One  general  opinion  concerning  the  magnesian  compounds  in 
cement  is  that  they  cause  the  first  or  preliminary  setting  of  the 
cement,  but  that  they  expand  and  crack  after  aging.  In  all  cases 
the  calcic  compounds  are  considered  to  be  the  ones  which  harden 
with  age,  and  they  are  the  compounds  which  cause  ultimate 
strength.  On  account  of  this  possibility  of  blowing,  it  is  there- 
fore the  common  practice  at  present  to  limit  the  presence  of  mag- 
nesia to  5  per  cent.  Cements  containing  up  to  this  limit  have  not 
been  shown  to  be  inferior. 

Another  theory  as  to  the  first  or  quick  setting  properties  of 
cement  attributes  these  properties  to  the  presence  of  calcium- 
aluminate,  and  the  final  or  ultimate  strength  to  the  calcium- 
silicate  only.  It  is  difficult  to  reconcile  these  conflicting  opinions. 

Other  chemical  elements  which  appear  in  a  cement  are  be- 
lieved to  be  of  no  practical  importance,  and  none  other  will  be 
considered,  except  plaster  of  Paris  or  sulphate  of  lime,  CaSO4, 
which  is  added  in  percentage  never  exceeding  2  per  cent.,  for  the 
purpose  of  causing  a  slower  setting  of  the  cement.  This  is  a 
common  practice,  and  its  effect  on  the  strength  of  the  cement  will 
be  considered  later. 


Art.  2. — Chemical  Analyses. 

It  will  be  interesting  to  examine  the  different  chemical  com- 
positions of  cement  as  they  have  been  recorded  by  different 
analysts.  It  will  be  found  that  the  variations  of  the  different 
constituents,  on  the  whole,  are  very  slight. 

Portland  Cements — Table  I.  exhibits  the  values  of  analyses  as 
taken  from  the  report  of  the  Watertown  Arsenal  "Test  of  Metals, 
etc.,"  for  1901. 


CHEMICAL  PROPERTIES  OF  CEMENT. 


[Ch.  I. 


TABLE  I.— PORTLAND  CEMENTS. 


Brand 

Location  of  Works 

| 

CO 

"o 

V 

3  G 
X  0 

Oi 

Alumina 

<L> 

j 

Hi 

Magnesia 

t.    4> 

3-0 

•as 
& 

Carbon 
Dioxide 

SiO2 

Fe203 

A12O3 

CaO 

MgO 

SO3 

CO2 

Alpha 

Easton,  Pa  
Northampton,  Pa  .  . 
WestCoplay,  Pa-- 
Siegfried,  Pa  

Akron  NY 

20.60 
18.32 
23.84 
22.00 
22.45 
22.94 
20.30 
20.42 
20.04 
22.92 

2.91 
3.36 
1.30 
2.50 
2.53 
2.90 
2.95 
2.10 
3.95 
2.46 

11.20 
11.22 
8.12 
9.00 
9.27 
6.30 
10.87 
11.00 
7.48 
7.98 

59.00 
60.00 
61.58 
59.90 
60.27 
43-74 
62.15 
57.50 
63.02 
63.39 

3-25 
3.78 
2.48 
3.50 
3.59 
*20.72 
2.51 
2.53 
1.23 
Trace 

1.40 
1.40 
1.60 
1.98 
0.60 
2.83 
1.  10 
2.26 
1.62 
1.28 

.34 
.92 
.08 
0.75 
.00 
.00 
0.12 
4-19 
3.00 
1.97 

Atlas 

Lehigh      

Star  (with  plaster)  .  . 
Star  (without    "   )•  • 

Whitehall    

Cementon,  Pa-  .  . 
Germany   

Alsen  

Dyckerhoff  
Josson  

Belgium  

21.38 

2.70 

9.  23  \  60.  76 

2.54  I.6I 

1.64 

':Not  included  in  average. 


TABLE  II.— PORTLAND  CEMENTS. 


Brand 

Location  of  Works 

Si02 

AloO3 

FeoOs 

CaO 

MgO 

S03 

Alpha 

22.62 
21.96 
19-92 
22.68 
21.08 
22.04 
21.86 
21.8 
23.08 
20.95 
22.93 

8.76 
8.29 
9.83 
6.71 
7.86 
6.45 
7.17 
7.95 
6.16 
9.74 
^—10 

2.66 
2.67 
2.63 
2.35 
2.48 
3-41 
3.73 
4.95 
2.9 
3.12 
.33-^ 

61.46 
60.66 
60.32 
62.3 
63.68 
60.92 
61.14 
61.9 
62.38 
63.17 
64.67 

2.92 
3.43 
3.12 
3.14 
2.62 
3.53 
2.34 
1.64 
I.2I 
.75 
.94 

.53 
.43 
.13 
.88 
.25 
2.73 
1.94 
.79 
1.66 
.86 
1.05 

Atlas  
Giant  
Saylors  
Vulcanite  
Empire  

Jordan    NY 

Coplay   Pa  

Vulcanite    N.  J  

Warner    N.Y  

Diamond  
Sandusky  
Bronson  
Whitecliffs-.-. 

Middlebranch,  Ohio  

Bronson,  Mich  
Whitecliff,  Ark  

Average  .  . 

21.90 

7.89 

3.09 

62.04 

2.33 

1.49 

TABLE  III.— EUROPEAN  PORTLAND  CEMENTS. 


Brand 

SiO2 

A1203 

Fe203 

CaO 

MgO 

SO* 

White  label,   Alsen  

20  48 

7  28 

3.88 

64  3 

1.76 

2  46 

Dyckerhoff 

20  64 

7  15 

?  69 

63  06 

2  33 

39 

Germania  

22  08 

6  84 

3  36 

63  72 

32 

82 

Hemmoor   

21  14 

5  95 

4  oi 

63  24 

44 

47 

Lagerdorfer  

23  55 

7  47 

2  4 

61  99 

42 

07 

Brook,  Shoobridge  &  Co 

22  2 

7  3") 

4  77 

61  46 

35 

87 

22  18 

8  48 

5  08 

61  44 

34 

56 

Condor  

23  87 

6  91 

2  27 

64  49 

04 

88 

Candlot    Prench 

22  3 

85 

"3.    \ 

62  8 

45 

7 

Boulogne    French 

22  3 

7 

2  *) 

64  62 

I  04 

75 

Average 

22  07 

7  OQ 

0     KT 

63  12 

I  3*1 

I  40 

Art.  2.] 


CHEMICAL  ANALYSES. 


Table  II.  shows  similar  quantities  obtained  from  analyses  of 
American  cements,  compiled  by  Ries  &  Eckels,  in  "Lime  and 
Cement  Industries  of  New  York,"  1901,  page  705. 

Table  III.  is  taken  from  the  same  book  and  exhibits  the  com- 
position of  some  European  Portland  cements. 

TABLE   IV. 


CaO 

Si02 

A1203 

FeaOs 

MgO 

SO3 

60.94 

23.23 

7.75 

3.04 

2.14 

1.56 

Table  IV.  shows  the  average  results  of  chemical  analyses  made 
on  thirty-eight  samples  of  cement  used  in  submarine  work  on  the 
Charlestown  bridge,  Boston,  by  the  Boston  Transit  Commission, 
as  published  in  their  report  for  1900. 

Finally,  owing  to  the  interest  which  has  been  aroused  by  the 
novel  conditions  of  manufacture,  Table  V.,  containing  an  analysis 
of  the  Edison  Portland  Cement  Company's  cement,  is  given. 
The  analysis  is  taken  from  a  reported  test  by  Lathbury  &  Spack- 
man,  Incorp.,  of  Philadelphia,  and  was  published  in  the  "Engi- 
neering Record"  December  26,  1903. 

TABLE  V. 


CaO 

SiO2 

A12O3 

Fe203 

MgO 

62.71 

20.14 

7.51 

3.33 

2.34 

These  tables  show  very  uniform  results;  in  general,  the  per- 
centages of  the  constituents  are  as  follows : 


CaO 

MgO 

SiO2 

A1203 

Fe9O, 


averages 


62% 

2% 

22% 
8% 

3% 


Inserting  these  values  in  the  Newberry  formula,  the  result  ob- 
tained is 


CHEMICAL  PROPERTIES  OF  CEMENT. 


[Ch.  I. 


2.8X22+i.iX8=i 

62 

or  an  error  of  14  per  cent,  as  compared  with  a  theoretically  per- 
fect cement. 

By  substitution  the  first  of  Le  Chatelier's  formulas  reduces  to 
62+2 


and  the  second  to 


22+8 

62+2 


=2.13; 


-5-82 


22—8—3 

These  values  are  respectively  smaller  and  greater  than  3,  as 
they  should  be;  but  they  give  no  indication  of  the  standard  of  ex- 
cellence obtained. 

Natural  Cements — The  following  tables  show  the  average  an- 
alyses of  both  European  and  American  natural  cements : 

Table  VI.  is  taken  from  the  Watertown  Arsenal  report  on 
"Test  of  Metals"  for  1901;  Table  VII.  from  U.  Cummings's 

TABLE  VI.— NATURAL  CEMENTS. 


Brand 

Location  of  Works 

SiO2 

Fe2O3 

AloO3 

CaO 

MgO 

SO3 

C02 

Akron  Star     

Akron,  N.Y  
Mankato,  Minn. 
Siegfried,  Pa.  ... 
Rosendale,  N.  Y. 
Mankato,  Minn.  . 
Whiteport,  N.Y.. 
Binne  water,  N.Y. 
Akron,  N.Y..... 

20.40 
19.02 
30.40 
25.00 
27.70 
28.71 
26.66 
23.70 
32.00 

2.56 
1.24 
2.60 
2.27 
1.86 
3.60 
3.02 
3.30 
2.70 

6.22 
8.96 
10.36 
8.93 
7.06 
5.88 
11.48 
16.70 
8.79 

40.64 
41.18 
52.12 
39.30 
37.00 
27.00 
38.33 
37.00 
33-89 

25.80 
26.58 
0.21 
16.18 
22.63 
30.00 
16.41 
15.30 
18.10 

2.91 
.27 
.24 
.40 
.23 
.30 
.35 
.98 
.31 

1.47 
1.75 
3.07 
2.66 
2.46 
3.52 
2.75 
2.00 
3.20 

Austin  

Bonneville  Improved.  . 
Hoffman* 

Newark  &  Rosendale.  . 
Norton.          .          

Obelisk  

Potomac  

25.95 

2.57 

9.37 

38.49 

19.02 

1.55 

2.54 

^Contains  4.26  per  cent,  of  Oxides  of  Sodium  and  Potassium. 

"American  Cements,"  and  Table  VIII.  from  analyses,  reported 
by  D.  J.  Whittemore,  in  the  Transactions  of  the  American  Society 
of  Civil  Engineers,  1880. 

The  American  natural  cements  of  Table  VII.  cover  a  wide 
range  of  territory. 


Art.  2.] 


CHEMICAL  ANALYSES. 


TABLE  VII.— NATURAL  CEMENTS.* 


Brand  and  Location  of  Works. 

SiO-2 

Alo03 

Fe2O3 

CaO 

MgO 

Buffalo  Hydraulic  Cement  ;  Buffalo,  N.  Y  
Utica    HI                       

24.3 
34.66 
23.16 
26.4 
25.28 
30.5 
29.98 
30.84 
27.3 
27.98 
28.38 
19.9 
22.62 
26.69 
24-34 
23.32 
27.6 
33.42 
22.58 
22.44 
28.43 
22.21 
32.06 
28.45 
18.59 
28.02 
25-15 

2.61 
5.1 
6.33 
6.28 
7.85 
6.84 
6.88 
7.75 
7.14 
7.28 
11.71 
5-92 
7.44 
7.21 
8.56 
6.99 
10.6 
10.04 
7.23 
6.7 
6.71 
16.48 
21.27 
2.24 
9.14 
10.2 
8. 

6.2 
1.  71 

1.43 
2.42 
2.5 
2.  1  1 
1.8 
1.7 
2.29 
1.  14 
1.4 
1.3 
2.08 
5.97 
.8 
6. 
3.35 
2. 
1.94 
1.67 
2.  1  1 
2. 
I. 
8.8 
3.28 

39.45 
30.24 
36.08 
45.22 
44.65 
34.38 
33.23 
34.49 
35.98 
37.59 
43.97 
46.75 
40.68 
43.12 
61.62 
53.96 
33.04 
32.79 
48.18 
32.73 
36.31 
39.64 
35-56 
56. 
40.7 
44.48 
49-53 

6.16 
18. 
20.38 
9. 
9.5 
18. 
17.8 
17.77 
18. 
15. 
2.21 
16. 
22. 
19.55 
.4 
7.76 
7.26 
9.59 
15. 
.67 
23.89 
17.5 
7. 
10. 
27. 

13.78 

Milwaukee    Wis        

N    L    &C    Co  •  Rosendale    N   Y   

Rocklock*   Rosendale    N  Y      

N    Y    to  R  •    Ro«?«>ndnle    N    Y 

Hoffman*     Rr»<;c>ndale     NY 

Norton  High  Falls*   Rosendale    NY           

Brockett;  Ft.  Scott  Hydraulic,  Kansas  City,  Mo  

ITtim   Rrnnd'    Utirn     111 

^honhc>rH^tr»wn     W^    Va 

Hydraulic  Cem    Rock*   Platte  River    Neb 

St.  Louis  Hydraulic  Cement,  near  E.  Carondelet,  111. 

Warnock    Ohio                        •            

Round  Top  Cement*   Hancock   Md  

26.40 

8.17 

2.55 

41.12 

12.97 

"From  "American  Cements,"  by  U.  Cummings 


TABLE  VIII.— NATURAL  CEMENTS. 


Cement  No. 

CaO 

MgO 

SiO2 

A1203 

Fe203 

j 

45  17 

16.52 

23.40 

8.07 

2.45 

2                ... 

36.32 

14.47 

24.50 

14-32 

2.93 

3 

33.97 

15.21 

28.04 

12.82 

4.60 

4 

40.75 

25.25 

22.22 

8.68 

1.  18 

Average.  . 

39.05 

15.36 

24.54 

10.97 

2.79 

The  results  show  that 


CaO 

MgO 
SiO2 
A12O8 
Fe203 


averages 


40  % 

15  % 

26  % 


8  CHEMICAL  PROPERTIES  OF  CEMENT.  [Ch.  I. 

It  will  be  seen  that  the  greatest  difference  between  the  natural 
and  Portland  cement  is  in  the  varying  proportions  of  the  lime 
and  magnesia  contents;  the  other  constituents  remain  about  the 
same.  Using  the  average  figures  of  the  natural  cements  given 
on  the  preceding  page,  the  Newberry  formula  becomes 

2.8X26+i.iX8j= 

40 
the  first  of  Le  Chatelier's  formulas  becomes 

4°±I5=I.6 

26+8| 
and  the  second, 

=3.67 
3    7 


None  of  these  formulas  furnishes  results  comparable  with  theo- 
retic requirements,  in  the  case  of  the  Newberry  formula  probably 
on  account  of  the  neglect  of  the  magnesia. 

As  a  conclusion  it  is  evident  that  a  chemical  analysis  may  give 
no  final  indication  of  the  quality  of  the  cement.  Adulteration  of 
the  cement  with  inert  material,  such  as  slag,  may  be  discovered. 
Certain  materials,  such  as  magnesia  or  plaster  of  Paris,  may  be 
found  present  in  too  large  quantities;  but  it  seems  evident  that  a 
poor  cement  may  be  due  more  to  imperfect  manufacture  than  to 
the  use  of  improper  constituents. 


CHAPTER  II. 
PHYSICAL  TESTS  OF  CEMENTS. 

The  mechanical  operations  attending  the  manufacture  of  ce- 
ment, such  as  the  mixing,  burning  and  grinding  of  the  raw  ma- 
terials, bear  intimate  relation  to  the  final  physical  properties  of 
the  cement,  and  should  be  analyzed  just  as  closely  as  the  chemical 
compositions;  but  in  this  treatise  it  is  out  of  place  to  discuss 
manufacturing  operations.  The  manufacture  of  a  cement  is 
therefore  to  be  assumed  correct  if  a  sample  of  it  passes  those 
physical  tests  which  are  made  for  the  purpose  of  determining  its 
acceptance  or  rejectance  for  use.  These  tests  are  of  such  a  char- 
acter that  the  results  of  all  experimenters  are  comparable;  but  it 
is  not  necessary,  although  it  is  desirable,  that  these  tests  should 
furnish  values  of  the  strength  of  the  material,  values  which  might 
be  used  in  designing  engineering  work. 

Art.  3 — Commercial  Physical  Tests. 

The  phys.ical  tests  require  but  brief  explanation,  and  only  those 
tests  which  are  practiced  in  the  United  States  need  consideration. 
They  are  five  in  number: 

1.  Specific  gravity, 

2.  Fineness, 

3.  The  time  of  setting, 

4.  The  tensile  strength,  and 

5.  The  constancy  of  volume. 

They  are  fully  explained  in  the  reports  presented  on  January 
21,  1903,  and  on  January  20,  1904,  to  the  American  Society  of 
Civil  Engineers  by  its  Committee  on  "Uniform  Tests  of  Ce- 
ments." A  copy  of  these  reports  is  given  in  the  appendix. 

Experience  has  shown  that  good  cements  furnish  certain  re- 


10  PHYSICAL  TESTS  OF  CEMENTS.  [Ch.  II. 

suits  in  these  standard  tests,  and  it  is  to  be  expected  that,  if  new 
cements  fulfill  the  same  conditions,  their  behavior  in  construction 
work  will  be  the  same. 

Art.  4 — Specific  Gravity  Tests. 

As  stated  in  the  first  of  the  two  reports  mentioned  above,  the 
specific  gravity  of  a  cement  is  lowered  by  underburning,  adul- 
teration and  hydration ;  but  the  adulteration  must  be  in  consider- 
able quantity  to  affect  the  result  appreciably.  When  properly 
made,  this  test  affords  a  quick  check  for  underburning  or  adul- 
teration. 

Table  I.  exhibits  the  values  of  the  specific  gravity  of  repre- 
sentative Portland  and  natural  cements,  and  is  taken  from  the 
Watertown  Arsenal  Report  on  "Tests  of  Metals"  for  1901.  The 
determinations  were  made  with  a  Schumann  volumeter,  benzine 
being  the  liquid  employed. 

Brand  TABLE   I.  g^# 

Alpha  Portland  Cement 3- 1 1 

Atlas  Portland 3-09 

Storm  King  Portland 3.07 

Whitehall  Portland  (14  days  after  grinding) 3.13 

Alsen  Portland 3-08 

Dyckerhoff  Portland 3. 1 1 

Josson  Portland 3.04 

Bonneville  Improved  Natural  Cement 2.85 

Hoffman  Natural 3.06 

Norton  Natural 3-03 

Austin  Natural 3-15 

Mankato  Natural 2.93 

Newark  &  Rosendale  Natural  (12  days  after  grinding) . .  3.06 

Obelisk  Natural 3. 12 

Potomac  Natural 2.94 

It  will  be  seen  that  Portland  cements  give  uniform  results,  the 
average  of  seven  cements  being  3.09. 

The  specific  gravity  of  the  above  cements  after  they  had  set 
was  obtained  in  various  ways. 

Table  II.  shows  the  specific  gravity  of  the  reground  material 
after  the  cement  had  set  for  a  period  of  three  days.  Different 


Art.  4.] 


SPECIFIC  GRAVITY  TESTS. 


11 


percentages  of  water  were  used,  as  indicated.  It  will  be  seen 
that  in  general  the  larger  amount  of  water  reduces  the  specific 
gravity. 


TABLE  II. 


Brand 

Specific  Gravity.—  Material  mixed  with  percentages  of 
water  of 

5% 

10% 

15% 

20% 

30% 

40% 

Alpha  Portland             

2.94 
2.69 
2.83 

2.88 
2.73 
2.80 

2.69 
2.82 
2.73 
2.77 

2.75 
2.77 

2.59 
2.73 

2.77 
2.67 

Lyckerhoff  Portland  
Bonneville  Improved  Nat'l 
Mankato  Natural    

The  specific  gravity  of  the  hydrated  material  in  a  cake  of 
cement  was  also  determined,  as  shown  in  Table  III.  The  ma- 
terial was  weighed  both  in  air  and  in  water  by  means  of  a  chemi- 
cal balance,  account  being  taken  of  the  water  absorbed  when  the 
cement  was  immersed,  thus  making  the  necessary  correction  for 
voids.  The  cakes  of  material  in  this  case  were  halves  of  tensile 
briquettes,  but  the  report  does  not  give  the  age  of  the  briquettes; 
there  seems  to  be  no  difference  in  the  values  of  those  briquettes 
which  set  in  air  or  in  water. 

TABLE  III. 


Brand 

Specific  Gravity  of  Briquettes  Which 
Set  In 

Air 

Water 

Alpha    Portland      

2.23 
2.  1  1 
1.65 
1.79 
1.65 

2.29 
2.07 
1.66 
1.77 
1.66 
1.92  to  2.17 

Dyckerhoff    Portland  

Atlas  Portland  (Material  from  12  inch  Cubes).  . 

(it  will  be  seen  that  the  specific  gravity  of  the  cement  after  set- 
ting is  considerably  less  than  the  cement  before  the  addition  of 
water./ 

Article  5. — Fineness  Test. 

The  fineness  of  a  cement  indicates  to  a  great  degree  the  pro- 
portion of  inert  material  in  it.  Until  lately  it  has  been  thought 
sufficient  to  measure  the  fineness  of  a  cement  with  a  No.  100 
sieve,  but  it  is  now  becoming  the  practice  to  use  a  No.  200  sieve. 


12 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


As  recommended  by  the  American  Society  of  Civil  Engineers, 
these  sieves  should  be  made  of  woven  cloth  of  brass  wire  which 
has  the  following  diameters : 

No.  100 0.0045  inches 

No.  200 0.0024  inches 

The  mesh  should  be  regular  in  spacing  and  be  within  the  follow- 
ing limits: 

No.    100 96  to  100  meshes  to  the  linear  inch 

No.  200 188  to  200  meshes  to  the  linear  inch 

The  sifting  is  continued  upon  a  sample  until  not  more  than 
one-tenth  of  i  per  cent,  passes  through  after  one  minute  of  con- 
tinuous sifting.  The  percentage  sifting  through  is  found  by 
weighing  the  residue  and  subtracting  from  the  original  quantity. 

There  is  naturally  a  commercial  limit  to  the  fineness  of  grind- 
ing of  a  cement;  the  following  tables  show  characteristic  results 
obtained  from  various  well  known  brands  of  Portland  and  natural 
cements. 

Table  I.  is  taken  from  the  Report  of  the  Watertown  Arsenal 
''Test  of  Metals,"  etc.,  1901 ;  chemical  analyses  made  on  the  dif- 
ferent sized  particles  of  these  brands  show  substantially  the  same 
composition  which  was  found  in  the  material  taken  from  the 
barrels. 

TABLE  I. 


Size  of  Grain 


Brand  of  Cement 

Greater  Than 
.0058  Inch 

.0050 

.0034 

.0027 

Smaller  Than 
.0027 

Corresponding  to  Sieve  Having  Meshes— 

98  x  100 

112x118 

155x170 

188x198 

Atlas  Portland  

II.  2 

12.9 
19.3 
14.  1 
33.6 
12.5 

3.8 
4-7 
5-7 
1.9 

9.1 

10.4 
7.9 
6.4 

6.6 
II.  4 
8.2 
12.5 
23.8 
17.5 

69.3 
60.6 
58.9 
65.1 
42.6 
70.0 

Star  Portland 

Alsen  Portland 

Hoffman   Natural  
Mankato  Natural  
Norton   Natural  

Table  II.  is  taken  from  Vol.  VI.  of 
covers  Portland  cements  only. 


'Mineral  Industry,"  and 


Art.  5.] 


FINENESS  TEST. 


13 


TABLE  II. 


Brand. 

Percentage  Passing  Sieve- 

No.  50 

No.  100 

No.  200 

100 
99 
99.5 
99.7 
99.6 
99.6 
98.8 
99.7 
100 
99.6 

96.4 
94.9 
92.7 
94.8 
95.3 
92.8 
88.3 
92.4 
•  99.6 
88.5 

68.4 
72.0 

Giant      

Atlas 

Alpha 

Brooks    Shoobrid^c  &  Co.  ...... 

Alsen                               

Aalborg        

As  a  matter  of  present  day  interest,  the  following  test  of  the 
Edison  Portland  Cement  Company's  cement,  from  the  same  re- 
port previously  mentioned,  may  be  noted: 

Passed  No.  100  sieve 99.8$ 

Passed  No.  200  sieve 91.6$ 

Although  two  cements  may  furnish  the  same  degree  of  fine- 
ness as  to  a  No.  100  sieve,  finer  sieves  may  show  different  results. 
German  experimenters  have  therefore  employed  the  velocities 
and  carrying  capacities  of  liquids  as  a  measure  of  fineness,  but 
such  refinement  in  testing  is  unnecessary.  The  No.  200  sieve 
furnishes  a  sufficient  test. 

The  tests  which  have  been  made  upon  cements  to  prove  the 
superiority  of  fine  grinding  are  not  of  great  importance,  and  even 
in,  some  cases  show  contradictory  results.  These  are,  however, 
easily  explained.  Neat  unsifted  cement,  for  instance,  may  show 
greater  strength  than  the  finely  sifted,  because  the  grains  in  the 
mixture  may  be  better  balanced,  or  because  the  coarser  material, 
which  is  the  harder  burned,  and  usually  the  better,  has  been  ex- 
cluded from  the  sifted.  In  the  case  of  mortars  the  proportions 
and  balancing  of  the  sand  greatly  outweigh  any  results  that  may 
be  obtained  due  to  the  sifting  of  the  cement  itself.  The  reader  is, 
however,  referred  to  experiments  by  Grant,  Vol.  XXL,  Proc. 
Inst.  Civ.  Eng.,  and  to  Clarke,  Trans.  Am.  Soc.  C.  E.,  Vol.  XIV. 

Art.  6.— Test  for  Time  of  Setting. 

Two  periods  are  noted  in  determining  the  time  of  setting  of  a 
cement:  the  initial  setting,  when  the  material  first  begins  to  set, 


14 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


and  the  final  setting,  when  the  material  has  acquired  a  certain 
degree  of  hardness.  The  former  period  determines  the  begin- 
ning of  the  process  of  crystallization,  and  is  important  to  deter- 
mine, as  a  disturbance  of  the  cement  after  the  time  of  this  initial 
setting  produces  loss  of  strength;  but  the  time  of  setting  never 
furnishes  a  gauge  as  to  the  ultimate  strength  of  a  cement. 

It  is  unnecessary  to  describe  the  apparatus  used  in  this  test; 
the  report  of  the  Committee  of  the  American  Society  of  Civil 
Engineers  records  in  detail  the  methods  of  operation. 

Table  I.,  taken  from  the  Watertown  Arsenal  Report,  1901, 
shows  some  characteristic  results  of  the  time  of  setting  of  some 
standard  American  cements,  when  gauged  with  different  per- 
centages of  water;  the  tests  were  made  according  to  both  Ameri- 
can and  German  standards.  The  differences  for  the  varying  per- 
centages of  water  are  quite  marked,  the  time  of  set  increasing 
with  the  amount  of  water.  There  is  also  considerable  difference 
in  the  results  of  the  two  methods  of  test.  In  general,  it  may  be 
said  that  natural  cements  set  faster  than  Portland. 


TABLE  I. 


Brand 

Water 

Gillmore's  Method 

German  Method 

Per  Cent. 

Initial  Set 

Final  Set 

Initial  Set 

Final  Set 

Alpha  (Portland)  \ 
Atlas  (Portland)  I 

Hoffman  (Natural).  .  .  .  < 

Newark  and  Roscndale  J 
(Natural)  1 

20 
25 
30 
20 
25 
30 
30 
35 
40 
35 
40 
45 

H.      M. 

2       20 
3       20 
5      40 
4      05 
5       10 
7      00 
2      15 
2      55 
3      43 
0      37 
0      47 
I      08 

H.      M. 

5       00 
7       30 

H.      M. 

0     35 

2       50 
4      40 
2      45 
3      35 
5      30 
I      25 
2      20 
2      48 
0      32 
0      40 
0      48 

H.      M. 

4       25 
6      35 
8      40 
6      10 
7      05 

7       10 
8      05 

3      25 
5      40 

2      55 
4      10 

I       17 
3      44 
4      18 

I      07 
2       19 
3      33 

Action  of  Plaster  of  Paris— The  time  of  setting  of  a  cement 
may  be  delayed  by  the  addition  of  a  small  percentage  of  plaster 
of  Paris.  The  action  in  that  case  is  merely  mechanical.  The 
plaster  of  Paris  dissolves  in  the  water  and  forms  a  protecting 
covering  about  the  cement  particles;  at  the  same  time  it  hardens 


Art.  6.] 


TEST  FOR  TIME  OF  SETTING. 


15 


and  prevents  action  of  the  water  on  the  cement.  In  small  per- 
centages, plaster  of  Paris  is  found  to  increase  the  strength  of  ce- 
ments, but  in  large  quantities  expansion  or  blowing  of  the  cement 
is  likely  to  occur.  The  action  in  that  case  is  similar  to  that  of 
sea-water  on  cement. 

E.  S.  Wheeler,  on  page  2938  of  the  Report  of  the  Chief  of 
Engineers,  U.  S.  Army,  for  1895,  records  numerous  tests  show- 
ing the  effect  of  plaster  of  Paris  on  the  time  of  setting.  An  ad- 
dition up  to  2  per  cent,  increases  both  the  periods  of  initial  and 
final  set,  but  an  addition  of  more  than  2  and  up  to  10  per  cent, 
decreases  this  period.  It  is  not  necessary  to  give  the  detailed 
figures  of  these  experiments. 

Table  II.  is  taken  from  the  Report  of  the  Chief  of  Engineers, 
U.  S.  Army,  for  1896,  p.  2832,  and  shows  the  varying  values  of 

TABLE  II. 

Tensile  Strength  of  Portland  Cement  with  Varying  Percentages  of 
Plaster  of  Paris.  The  sand  is  natural  Point  aux  Pins.  Each 
result  is  an  average  of  five  specimens. 


Plaster  of  Paris  to  Total  Cement 

Ratio  of  Cement 
to  Sand 

Strength  in  Lbs.  Per  Sq.  Inch  at  Age  of—  i 

7  Days 

6  Months 

1  Year 

0  per  cent   

:0 
:0 
:0 
:0 
:0 
:2 
;2 
:2 
:2 
1:2 

487 
626 
600 
519 
380 
323 
388 
360 
289 
192 

743 
746 
754 
742 
660 
492 
530 
547 
607 
663 

487 
515 
610 

588 
647 

3  per  cent     

6  per  cent  

the  tensile  strength  of  a  Portland  cement  with  the  addition  of 
various  percentages  of  plaster  of  Paris.  It  will  be  seen  in  gen- 
eral that  an  addition  of  plaster  of  Paris  up  to  2  per  cent,  has  no 
weakening  effect.  This  is  shown  both  for  neat  cement  and  for  a 
cement  mortar  of  I  part  of  cement  to  2  of  sand.  Again,  it  will 
be  seen  that  the  mortar  in  which  the  cement  contained  a  large 
amount  of  plaster  of  Paris  attained  considerable  strength  at  the 
age  of  one  year.  The  report  noted  records  tests  on  three  brands 
of  Portland  cements  and  on  some  natural  cements;  the  results 


16 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


are  similar  to  those  in  the  table;  but  many  of  the  natural  cements 
checked  and  disintegrated  before  the  time  of  testing.  The  effect 
of  the  addition  is  seen  to  give  very  variable  results,  but  a  safe 
limit  is  2  per  cent. 

The  time  of  setting  of  a  cement  depends  also  on  its  chemical 
composition  and  on  the  character  of  its  burning.  In  general,  a 
lightly  burned  cement  sets  quicker,  as  does  also  a  freshly  burned 
cement;  but  there  are  frequent  exceptions.  The  quantity  of 
water  used  in  gauging  the  cement,  the  temperature  of  the  water 
and  the  temperature  of  the  air  all  affect  the  time  of  setting.  A 
rise  of  temperature  follows  the  setting  of  all  cements,  and  this 
rise  increases  very  rapidly  for  fast  setting  cements.  The  time  of 
setting  is  also  affected  by  the  volume  of  cement  mixed. 

TABLE  III. 


Compressive  Strength   in 
Pounds  per  Square  Inch 
when  regauged  after  an 
interval  of  — 

Brand 

Alpha 
Portland 

Dyckerhoff 
Portland 

Star 
Portland 

Storm  King 
Portland 

1 

•-> 

1 

|l 

• 

3 
< 

Bonneville 
Natural 

Norton 
Natural 

Hours  After  First  Mixing 

0                   

7279 

3549 
3667 
3412 

3402 
2686 
2439 
2312 
1893 
1745 
1758 
1666 
1690 

3489 
3737 

3753 
3903 
3889 

1792 
1599 

1495 
II5I 

3328 
3498 

3827 
3696 

719 
724 

895 
387 

388 
*425 

713 
443 

340 
424 
378 

2 

6169 

7146 
6774 
6539 

•i 

4 

340 
276 

6       

8       

10     

12 

16 



1Q 





20  



*After  seven  hours. 

Temperature  Affects  Setting — Gen.  Gillmore,  in  his  Treatise  on 
Limes,  Mortars  and  Cements,  page  83,  shows  some  interesting 
results  as  to  the  variations  in  time  of  setting  due  to  changes  of 
temperature  of  water  used  in  mixing.  It  is  unnecessary  to  re- 
produce here  his  results,  but  he  shows  that  invariably  high  tem- 
peratures increase  the  rapidity  of  setting.  There  may  be  marked 
differences  in  the  variations  for  different  cements,  but  the  state- 


Art.  6.1 


TEST  FOR  TIME  OF  SETTING. 


17 


ment  is  true  of  all.  Exactly  similar  results  are  recorded  by  E. 
S.  Wheeler  in  the  Report  of  the  Chief  of  Engineers,  U.  S.  Army, 
1895,  page  2936. 

Retarding  the  Set — If  agitated  sufficiently,  it  is  possible  to  pre- 
vent a  cement  from  setting  at  all;  if  disturbed  after  the  final  set- 
ting has  commenced,  its  strength  is  greatly  decreased,  and  since 
natural  cements,  as  a  class,  reach  their  final  set  in  periods  of  time 
considerably  less  than  Portland  cements,  it  may  be  expected  that 
the  effect  of  regauging  the  natural  cements  is  of  greater  conse- 
quence. This  is  clearly  shown  by  Table  III.,  which  is  taken 

TABLE   IV. 


Ult.    Compressive    Strength 
in  Pounds  per  Square  Inch 
after  elapse  of  X  hours  be- 
tween    initial    mixing    and 
placing    of    material    in 
moulds 

Brand  of 
Cement 

Ult.    Compressive   Strength 
in  Pounds  per  Square  Inch 
after  elapse  of  X  hours  be- 
tween   initial    mixing    and 
placing    of    material     in 
moulds 

Brand  of 
Cement 

£ 

CO 

•0.2 
ga- 
•=j= 

£* 

S 

V) 

Star  Portland 
Without  Plaster 

Star  Portland 
With  Plaster 

Star  Portland 
Without  Plaster 

Hours 

Hours 

o 

5467 
4665 
6421 
5470 
2718 
2662 
2387 
2160 
2214 
2154 
1901 

2414 
2594 
2561 
2167 
2282 
2021 
1842 
1541 
1242 
1426 
1499 

24 

1669 
1442 
1279 
1132 
1  168 
1150 
1  00  1 
763 
723 
681 

1462 
1216 
IIOI 
1  143 
1069 
IIIO 
849 
834 
782 
737 

I 

30 

2             

36 

4  .     .  .         

42  . 

6    

")0  .  . 

8  

60  

10    

70  «  

12  

80  

14  

90  

16 

100 

20 

from  the  Watertown  Arsenal  Report  for  1901,  and  exhibits  the 
results  obtained  in  retarding  the  setting  of  cements  which,  after 
having  been  mixed  with  water,  were  left  undisturbed  until  each 
of  the  periods  shown,  when  a  sample  from  the  main  batch  was 
extracted. 

The  majority  of  these  specimens  were  6  inch  cubes,  although 
some  were  smaller  sized  cubes.  Many  of  the  results  obtained 
were  averages  of  two  or  more  samples,  and  the  average  age  of 
the  specimens  was  about  thirty  days.  In  this  set  of  experiments 
the  main  batch  of  the  cement  was  left  undisturbed  until  the  sam- 


18 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


pies  were  extracted,  when  the  entire  mass  wras  again  gauged  with 
water;  the  sample  was  then  tamped  into  a  mould  and  allowed  to 
set  without  further  interference. 

Table  IV.  shows  the  compressive  strengths  attained  when  the 
main  batch  of  the  cement  was  not  left  undisturbed  after  the  initial 
mixing,  but  kept  in  a  continual  state  of  agitation  in  the  mixing 
bed.  In  this  test  the  two  kinds  of  cement  used  were  both  Star 
Portland,  but  one  contained  plaster  of  Paris,  as  a  restrainer  to 
control  the  time  of  setting,  while  the  other  contained  no  plaster. 
The  effect  of  the  restrainer  is  clearly  shown. 

TABLE  V. 


Brand  of  Cement 

Percentage  of 
Water 

Maximum 
Temperature 
in  Degrees 
Centigrade 

Ultimate 
Compressive 
Resistance 
in  Pounds 
per  Sq.  Inch 

Age 
in 
Days 

Weight 
per 
Cu.  Ft. 
in  Lbs. 

Alpha  Portland  

26.2 

95- 

5706* 

9 

133  4 

Star  Portland  

26.5 

76. 

Storm  King  Portland.  . 
Whitehall  Portland 

27.0 
OK  o 

42.5 
ino  t 



— 



Dyckcrhoff  Portland  .  . 

25.0 
oq  7 

63. 
(;i 

1547 

13 

130.9 

Atlas  Portland  
Bonnevillc  Natural.  .  .  . 
Obelisk  Natural.  ...... 

22.7 
37.6 
35  0 

81.5 
39-5 
37  5 

4872 
840 

9 
13 

137.5 
116  7 

36  5 

74  o 

740 

g 

1  15  I 

Austin  Natural  

40.0 
44  6 

35-0 
40  0 

Norton  Natural  

41.8 

39.0 



— 



*Not  ruptured. 

Temperature  Changes  During  Setting — Table  V.  shows  the 
temperatures  acquired  by  cements  during  setting;  these  values 
have  been  abstracted  from  the  Watertown  Arsenal  Report  for 
1901.  Experiments  were  made  on  1 2-inch  cubes,  the  upper  sur- 
face being  exposed  to  the  air.  The  thermometer  bulbs  reached 
to  the  centre  of  the  cubes.  It  is  interesting  to  note  that  the 
highest  temperatures  were  reached  by  Portland  cements  as  a 
class,  in  some  cases  exceeding  the  boiling  point  of  water.  A 
number  of  hours  elapsed  before  the  maximum  temperature  was 
obtained,  generally  six  to  twelve  hours  for  a  neat  Portland  ce- 
ment, while  a  1:1  mortar  required  about  eighteen  hours.  At  the 
end  of  one  and  one-half  days  the  Portland  cements  still  remained 


Art.  7.]  TESTS  OF  TENSILE  STRENGTH.  19 

above  the  temperature  of  the  room,  but  the  natural  cements  had 
nearly  returned  to  the  temperature  of  the  room.  The  .cements 
which  reached  the  highest  temperatures  almost  invariably  showed 
the  sharpest  crests  in  the  curves  which  were  plotted  with  the 
times  and  temperatures  as  ordinates. 

It  is  probably  merely  a  matter  of  coincidence  that  the  highest 
temperatures  belonged  to  cements  showing  the  highest  ultimate 
compressive  resistance,  but  it  may  be  interesting  to  investigate 
this  point  more  fully  at  some  future  time.  The  difference  be- 
tween the  Portland  and  natural  cements  is  very  marked,  but  may 
be  due  partly  to  the  excess  of  water  used  in  mixing  the  samples. 

Temperature  changes  are  naturally  less  marked  when  a  cement 
is  mixed  with  sand  and  stone  than  when  neat,  but  they  are  still 
very  noticeable.  Experiments  regarding  these  changes  are  now 
in  progress  on  some  large  pieces  of  concrete  work,  but  the  results 
are  not  yet  public. 

Art.  7 — Tests  of  Tensile  Strength. 

The  test  of  the  tensile  strength  of  a  cement  is  the  decisive  test 
in  regard  to  its  acceptance  for  use,  even  though  in  the  majority 
of  building  operations  it  is  not  the  tensile  strength,  but  the 
crushing  strength  of  the  material,  which  is  desired.  It  may  be 
shown,  however,  that  these  two  resistances  bear  an  almost  fixed 
ratio  to  one  another,  and  since  the  tensile  tests  are  more  easily 
made  and  require  less  expensive  apparatus,  they  have  practically 
displaced  the  crushing  tests. 

The  tests  are  made  on  small  briquettes  of  standard  form  whose 
minimum  area  of  cross-section  is  one  square  inch;  these  bri- 
quettes are  formed  both  from  the  neat  cement  and  from  mixtures 
of  the  cement  with  various  percentages  of  standard  or  normal 
sand,  and  they  are  tested  at  stated  periods  after  making.  The 
periods  are  usually  one,  seven  and  twenty-eight  days. 

The  tests  which  are  made  to  determine  the  tensile  strength  of 
cement  have  often  been  criticised  on  account  of  the  poor  form  of 
cross-section  of  the  briquette,  and  on  account  of  the  use  of  a  class 
of  sand  which  is  never  employed  in  practice.  Although  errone- 
ous values  of  the  actual  strength  of  the  cement  in  working  prac- 


20 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


tice  are  thus  found,  a  standard  of  comparison  between  different 
cements  is  still  obtained. 

It  is  unnecessary  to  describe*  any  of  the  apparatus  or  any  de- 
tails of  the  methods  of  operation.  The  following  figures  and 
tables  are  of  interest  as  showing  characteristic  results  of  tests 
made  on  the  tensile  strength  of  various  kinds  of  cement,  and  are 
given  for  the  purpose  of  determining  a  point  in  the  life  of  a 
cement  when  its  strength  ceases  to  show  an  increase  at  an  ap- 
preciable rate. 

TABLE  I. 

TENSION    EXPERIMENTS 


Age 

1  Cement 
OSand 

1  Cement 
OSand 

1  Cement 
3  Sand 

1  Cement 
3  Sand 

1  Cement 
5  Sand 

1  Cement 
5  Sand 

Immersed 

Not 
Immersed 

Immersed 

Not 
Immersed 

Immersed 

Not 
Immersed 

Ultimate  Resistance  in  Pounds  per  Square  Foot. 

7  days  

515 
6^8 
697 
814 
765 
838 

642 
651 
600 
638 
575 
507 

277 

350 
457 
487 
550 
503 

301 
438 
538 
605 
703 
650 

127 
180 
233 
281 
271 
270 

131 
247 
335 
410 
442 
408 

28  days 

84  days 

I  year  
2  years  

Gauged  with  .  .  . 

23  % 

10.  1  % 

9.5^  water 

COMPRESSION    EXPERIMENTS 


6320 

6200 

2570 

2930 

1210 

1260 

28  days 

8400 

8050 

3520 

4360 

1560 

I960 

84  days 

1  1  200 

9700 

5100 

5750 

1910 

•57  JO 

13000 

12200 

5280 

6160 

2150 

3200 

I  year   

I4I80 

14200 

6520 

7720 

2150 

3560 

2  years  

14700 

14800 

6000 

7100 

2450 

3500 

Table  I.  shows  the  results  of  two  sets  of  experiments  made  at 
the  Laboratory  de  1'Ecole  des  Fonts  et  Chaussees,  under  date  of 
February  6,  1896,  and  published  by  Berger  &  Guillerme  in  "Ci- 
rri ent  Arme."  The  values  given  are  all  the  mean  of  five  or  six 
specimens. 

In  the  first  series  of  experiments  the  briquettes  were  exposed 
to  damp  air  for  twenty-four  hours  and  then  immersed  in  fresh 
water;  in  the  second  series  there  was  no  immersion.  The  cross- 


*See  Appendix. 


or  THE 
I'NHVERSITY 


C'f 

•  H 


Art.  7.] 


OF  TENSILE  STRENGH. 


21 


section  qf  the  specimens  varied  from  0.78  to  1.2  square  inches. 
The  lower  part  of  the  table  is  inserted  to  show  the  ratio  between 
tensile  and  compressive  stresses  for  mixtures  of  the  same  kind. 

Figure  i  was  plotted  from  results  published  by  E.  C.  Clarke,  in 
Vol.  XIV.,  1885,  of  the  Transactions  of  the  American  Society  of 
Civil  Engineers,  and  shows  the  strength  obtained  by  Portland 
and  natural  cement  and  mortar  briquettes  whose  minimum  area 
of  cross-section  was  2j  square  inches.  Twenty  different  brands 


12  Months 
Age 
FIG.  l.-CLARKE'S  TESTS. 

of  cement  were  used,  and  the  figure  represents  25,000  breakings. 
The  ordinary  cement  briquette  has  a  minimum  area  of  I  square 
inch,  but  comparative  tests  made  at  the  time  showed  little  dif- 
ference in  result  between  cross-sections  of  i  and  2j  square  inches. 
Figure  2  shows  the  results  obtained  in  tensile  tests  on  four 
brands  of  Portland  cement,  as  published  in  the  report  for  1895  of 
M.  L.  Holman,  Water  Commissioner  of  St.  Louis;  each  plotted 
point  represents  an  average  of  ten  briquettes.  The  briquettes 
were  all  i  cement  to  3  normal  sand  and  were  left  one  day  in  air 


22 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 

and  the  remainder  of  the  time  in  water.     The  figure  shows  a 
continual  increase  in  the  strength  of  the  briquettes  for  the  period 


6  Months        l  Year 


2  Years 


3  Years 


3fc  Years 


Age  of  Specimens. 
FIG.  2.— HOLMAN'S  TESTS. 


of  3J  years  shown;  but  a  similar  series  of  tests  made  upon  neat 
cement  briquettes  showed  a  slight  decrease  after  the  end  of  one 

500 


iOO 


100 


1:4 


1:6 


1  Month  i  Year 

Age  of  Specimens. 
FIG.  3.— CLARKE'S  TESTS. 


8  Years 


year,  the  greatest  decrease,  as  compared  to  the  maximum  strength 
obtained,  being  about  20  per  cent.     It  is  only  proper  to  note  that 


Art.  7.] 


TESTS  OF  TENSILE  STRENGTH. 


23 


FIG.  4,-RAFTER'S  TESTS. 


briquettes,  when  one  year  old  or 
over,  become  very  brittle  and  may 
show  erratic  results  in  the  testing 
machine. 

Figure  3  shows  the  results  ob- 
tained by  E.  C.  Clarke,  as  part  of  the 
same  experiments  mentioned  pre- 
viously, in  which  he  found  the  varia- 
tion in  the  strength  of  cements  when 
mixed  with  increased  proportions  of 
sand.  These  tests  were  all  made  on 
one  single  brand  of  cement  and  rep- 
resented 500  breakings*. 

Figure  4  shows  the  strength  at- 
tained by  a  Portland  cement  both  at 
various  ages  and  when  mixed  with 
different  volumes  of  sand.  Each 
point  marked  on  the  curves  repre- 
sents an  average  of  five  briquettes. 
These  tests  were  made  by  Mr. 


.900, 


800 


600 


500 


100 


IT* 


100  200  300  400 

Age  in  Days. 
FIG.  5. 


24 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


George  W.  Rafter  and  are  published  in  the  annual  report  of  the 
"State  Engineer  of  New  York"  for  1894. 

Figure  5  is  taken  from  Johnson's  "Materials  of  Construction," 
page  575,  and  shows  the  average  tensile  strength  acquired  at 
various  ages  by  many  samples  of  one  brand  of  American  Port- 
land cement,  as  reported  by  Messrs.  R.  W.  Hunt  &  Co. 

R.  W.  Lesley  published  in  the  Journal  of  the  Association  of 
Engineering  Societies,  1895,  the  results  of  long  time  tests  made 
on  samples  of  cement  representing  300,000  barrels  of  the  Giant 


2  Years  3  i 

Age  of  Specimen  in  Years 

FIG.  6,-LESLEY'S  TESTS. 


Portland  brand  of  cement.  Figure  6  is  plotted  from  these  results, 
and  represents  a  series  of  tests  made  on  50,000  barrels  of  cement 
used  on  the  Sodom  and  Bog  Brook  dams  of  the  New  York  aque- 
duct. The  results  there  shown  are  characteristic  of  the  entire 
series.  Each  point  plotted  is  an  average  of  1,000  to  1,300  bri- 
quettes. Taking  only  the  tests  made  on  briquettes  of  one  cement 
to  three  sand,  it  will  be  seen  that  the  strength  at  three  months 
and  six  months,  as  compared  to  five  years,  are  respectively  60  per 


Art.  7.] 


TESTS  OF  TENSILE  STRENGTH. 


25 


cent,  and  73  per  cent.;  and  for  three  months  and  six  months,  as 
compared  to  one  year,  respectively  82  per  cent,  and  100  per  cent. 
Figure  7  shows  the  results  of  experiments  recorded  by  J. 
Grant  in  the  Proceedings  of  the  Institution  of  Civil  Engineers, 
Vol.  XXXI I. ,  page  280,  and  shows  the  variation  in  the  tensile 
strength  of  Portland  cement  briquettes  from  observations  extend- 
ing over  a  considerable  number  of  years.  The  form  of  specimen 
used  was  not  the  standard  form  as  used  to-day,  the  minimum 
area  of  cross-section  being  2\  square  inches.  The  specimens 
were  all  kept  in  water  from  the  time  of  making  until  the  time  of 
testing,  and  ten  specimens  were  tested  at  each  age.  It  will  be 


fi-S 

a  £ 


^—  ••' 

I  Portland  Cement  Neat 

/ 

*** 

1  :   Th 

lines     \ 

Jand  1; 

f 

1200 


800 


Age  in  Years 
FIG.  7.— GRANT'S  TESTS. 

seen  that  there  is  no  increase  of  strength  after  two  years.  For 
neat  specimens  the  percentage  of  increase  gained  after  three 
months'  age  is  20  per  cent.,  as  compared  to  the  final  strength; 
and  for  the  one  cement  to  one  sand  mortar  the  corresponding 
percentage  is  33.  Similarly,  comparing  the  increase  in  strength 
after  six  months  to  the  final  strength,  these  percentages  become 
respectively  1 1  and  22. 

The  following  table  shows  the  tensile  strength  of  the  Edison 
Portland  Cement  Company's  cement,  and  is  inserted  as  a  matter 
of  interest  as  giving  the  tensile  resistance  of  the  latest  cement  on 
the  American  market;  the  tests  are  taken  from  the  report  already 
mentioned. 

Neat,     I  day  =325  Ibs.  per  sq.  in.     Average  of  5  specimens. 
Neat,     7  days=676  Ibs.  per  sq.  in. 

1:3,    7  days=255  Ibs.  per  sq.  in. 

1:3,  28  days=33I  Ibs.  per  sq.  in. 


26  PHYSICAL  TESTS  OF  CEMENTS.  [Ch.  II. 

In  all  these  figures  it  is  seen  that  cement  and  the  cement  mix- 
tures attain  a  strength  not  differing  greatly  from  the  ultimate 
strength  within  a  period  of  three  months  from  the  time  of  set- 
ting, and  practically  that  within  a  month  or  so  after  this  period 
no  appreciable  change  in  the  strength  takes  place. 

It  is  important  to  recognize  this  fact  in  order  to  appreciate 
that  it  will  make  no  sensible  difference  in  tests  of  cement  mix- 
tures when  the  age  of  the  specimen  is  in  the  neighborhood  of 
three  months.  The  results  so  obtained  need  no  correction  for 
age  and  will  all  be  comparable. 

It  is  of  interest  to  record  the  following  empirical  formula  which 
has  been  proposed  by  W.  C.  Unwin  (Proc.  Inst.  Civ.  Eng.,  Vol. 
LXXXIV.)  for  determining  the  tensile  strength  of  a  briquette 
within  two  years  after  making;  he  derived  it  by  analyzing  the  re- 
sults of  tests  by  Bauschinger,  Grant,  Clarke  and  others. 

If  y  is  the  strength  of  a  cement  or  mortar  at  x  weeks  after  mix- 
ing, and  #  the  strength  of  the  same  in  pounds  per  square  inch  at 
seven  days,  then 

y=a-\-b  (x — i)n 

The  constant  n  has  values  which  can  be  assigned  beforehand, 
and  the  constant  b  is  determined  by  experiment  on  pieces  more 
than  one  week  old.  Unwin,  assuming  for  the  case  of  tension 
n  to  be  J,  finds  that  b  varies  within  rather  narrow  limits. 

Art.  8. — Ratio  of  Compressive  and  Tensile  Strengths. 

The  ratio  of  compressive  and  tensile  strength  is  not  a  constant 
quantity  for  all  ages  of  a  mortar,  since,  in  general,  compressive 
strength  increases  faster  than  the  tensile  strength;  but  experi- 
ments show  that  the  variation  of  this  ratio  is  not  very  great. 

J.  B.  Johnson  in  "Materials  of  Construction"  analyzes  the  re- 
sults of  numerous  experiments  on  a  mortar  of  one  cement  to 
three  sand,  which  were  recorded  by  Tetmajer  in  his  "Communi- 
cations," Vol.  VI.,  and  expresses  the  ratio  between  these  strengths 
by  the  following  equation : 

R=8.64+i.8  log  A 
where  R  represents  the  ratio  between  the  compressive  strength 


Art.  8.] 


RATIO  OF  COMPRESSION  TO  TENSION. 


27 


and  the  tensile  strength,  and  A  is  the  age  of  the  cement  mortar  in 
months. 

Busing  and  Schumann,  in  "Der  Portland  Cement,"  1899,  pre- 
sent in  Table  I.  results  which  furnish  the  relations  between  these 
two  kinds  of  stress.  The  specimens  were  made  with  ordinary 
sand  and  gauged  with  different  percentages  of  water,  and  were 

TABLE  I. 


Age 
in 
Days. 

10  Per  Cent.  Water 

1  2  per  Cent.  Water 

15  per  Cent.  Water 

Pounds  per  Sq.  In. 

Ratio 

Pounds  per  Sq.  In. 

Ratio 

Pounds  per  Sq.  In. 

Ratio 

Tension 

Com- 
pression 

Tension 

Com- 
pression 

Tension 

Com- 
pression 

7  
28  

284 
370 
407 
456 

2860 
4050 
5050 
5400 

10.  1 
10.9 
12.4 
II.  8 

196 
326 
366 
380 

1550 
2270 
2940 
3200 

7.8 
7.0 
8.0 
8.4 

143 

260 
328 
321 

781 
1420 
2130 
2410 

5.4 
5-5 
6.5 
7.5 

90  

180  

tested  at  various  ages.  It  is  to  be  noted  that  with  the  increase 
of  water  the  compression  decreases  faster  than  the  tension,  and 
that  with  the  increase  of  age  the  compression  tends  to  resume  its 
former  relations. 

TABLE  II. 


Age  in  Weeks 

Mixture 

Tension 

Compression 

Bending 

Shear 

Ult.  Resistance 
Pounds  per 
Square  Inch 

Ult.  Resistance 
Pounds  per 
Square  Inch 

Extreme  Fibre 
Stress  in  Lbs. 
per  Sq.  Inch 

Ult.  Resistance 
Pounds  per 
Square  Inch 

Specimens  Hardened  in 

Air 

Water 

Air 

Water 

Air 

Water 

Air 

Water 

{ 

I 

:0 
:3 
:5 
:0 
:3 
:5 
:0 
:3 
:5 

231 
106 
68 
266 
148 
119 
257 
244 
177 

224 
95 
64 
294 
169 
103 
292 
272 
232 

I860 
920 

543 
2460 
1500 
962 
3400 
2080 
1510 

1910 
880 
537 
2490 
1040 
977 
4680 
3340 
2960 

695 
273 
168 
860 
392 
284 
1010 
748 
545 

625 
247 
158 
887 
381 
276 
1350 
973 
810 

276 
109 
81 
316 
182 
136 
388 
294 
248 

271 
116 
77 
346 
181 
131 
415 
375 
364 

I 
104  to  113.  | 

An  exceedingly  interesting  set  of  experiments  was  published 
as  long  ago  as  1879,  by  Bauschinger,  in  the  Proceedings  of  the 
Munich  Technical  Institute,  Bauschinger  experimented  on  mor- 
tar specimens  of  I  cement  to  o  sand,  I  cement  to  3  sand,  and  I  ce- 


28 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


ment  to  5  sand.  His  tension  specimens  had  a  cross-section  of 
2.4X4-8  ins.  =  11. i  sq.  ins.  The  compression  specimens  were 
cubes  4.8  inches  on  the  side,  and  his  flexure  tests  were  made  on 
specimens  2.4X4.8X12  inches  long,  tested  with  a  span  of  10 
inches.  The  4.8  inch  side  was  vertical.  Tests  of  the  shearing 
resistance  were  made  on  the  flexure  specimens. 

Table  II.  shows  results  of  all  these  tests,  each  value  shown 
being  an  average  of  9. 

The  extreme  limits  of  the  ratio  of  compression  and  tension 
will  be  found  between  13.2  and  8.00  for  dry  specimens,  and  16.02 
to  7.35  fcr  the  wet.  It  is  to  be  noted,  however,  that  this  value 
of  16.02  was  exceptional,  the  next  highest  ratio  being  12.76. 
The  limits  of  the  ratios  of  the  ultimate  fibre  stress  in  flexure  to 
maximum  tensile  stress  were  3.93  to  2.46  for  the  dry,  and  4.65  to 
2.25  for  the  wet.  The  limits  of  the  ratios  between  shear  and  ten- 
sion were  1.51  to  1.03  and  1.57  to  I.Q7  for  the  dry  and  wet  re- 
spectively. 

TABLE  III. 


Gauged  with 

Gauged  with 

Gauged  with 

20  per  Cent.  Water 

22  per  Cent.  Water 

25  per  Cent.  Water 

Age  in 

«    J5 

c 

w      c 

c 

W       J3 

c 

1«2$ 

e  d- 

1.8  5 

C  9 

~  C  CT 

c  a 

||  I 

6  *>« 

||| 

Ratio 

III 

ill 

Ratio 

If! 

2  u  co 

s§5 

Ratio 

Air. 

Water. 

Days. 

Days. 

8l5 

B  fl  JS 

Hcfl-J 

U<E:J 

H^5  j 

#«3 

!  



717 

196 

3.7 

595 

189 

3.1 

430  * 

190 

2.3 

7  



3040 

354 

8.6 

3260 

392 

8.3 

2610 

402 

6.5 

28  



3990 

566 

7.1 

3760 

457 

8.2 

3130 

450 

7.0 

I  

6 

4250 

780 

5-5 

4720 

666 

5.8 

3880 

329 

IL8 

I  

27 

7370 

906 

8.1 

6870 

866 

7.9 

7580 

758 

10.0 

Table  III.  furnishes  values  of  the  ratio  between  tensile  and 
compressive  stresses,  and  is  taken  from  the  Watertown  Arsenal 
Report  for  1902.  The  specimens  were  all  of  neat  Peninsular 
Portland  cement.  Ten  specimens  of  each  kind  were  tested,  with 
varying  percentages  of  water  and  at  different  ages.  The  ratios 
of  the  two  kinds  of  stress  are  given  in  the  table.  The  tensile 
specimens  were  of  the  standard  form;  although  not  so  stated,  it 
is  probable  that  the  crushing  tests  were  made  on  the  broken 
halves  of  the  tensile  specimens. 


Art.  9.]      VARIATIONS  IN  THE  MAKING  OF  TENSILE  TESTS.  29 

Reviewing  all  these  experiments,  it  is  seen  that  it  will  never 
be  far  from  wrong  to  assume  the  ratio  between  ultimate  com- 
pression and  tensile  resistances  as  about  10;  although  it  should 
be  noted  that  all  the  tensile  tests  were  made  on  specimens  of  a 
form  which  probably  give  too  high  values. 

Art.  9.— Variations  in  the  Making  of  Tensile  Tests. 

The  author  does  not  believe  it  to  be  of  any  importance  to  con- 
sider in  any  detail  questions  bearing  on  variations  in  the  manner 
of  making  tensile  tests.  Under  this  heading  may  be  included 
the  variation  in  the  rate  of  loading  a  specimen;  the  testing  of  a 
specimen,  either  dry  or  wet,  or  an  appreciable  length  of  time 
after  taken  from  the  storage  tanks ;  the  variations  in  the  strength 
due  to  mixing  with  different  percentages  of  water;  the  effect  of 
temperature  changes  of  the  water  in  the  immersing  tanks;  the 
effect  of  salt  water  in  these  tanks;  the  period  elapsing  before 
placing  the  briquettes  in  water  after  making,  whether  twenty- 
four  hours  or  immediately  upon  setting  hard;  the  methods  of 
filling  the  moulds,  whether  by  ramming  or  by  slightly  tamping; 
the  time  employed  in  mixing  the  materials  in  the  dry  state  or  in 
the  wet  state;  the  eccentricity  of  a  specimen  in  the  clips  of  the 
testing  machine;  the  filling  of  the  molds  with  dry  cement,  and 
then  adding  water,  etc. 

The  results  of  the  tensile  tests  are  made  simply  a  basis  of  com- 
parison for  accepting  or  rejecting  offered  cements,  and  although 
the  questions  noted  do  affect  the  results  appreciably,  under 
standard  conditions  of  making,  the  personal  equation  of  the 
operator  will  be  a  factor  of  greater  importance  than  anything 
else.  Certain  points  depending  on  comparative  results  may, 
however,  be  determined  in  the  tensile  tests  of  briquettes,  of 
which  the  following  is  the  most  important,  namely,  the  advan- 
tages to  be  gained  by  the  use  of  one  of  several  possible  sands. 
A  choice  between  different  sands  offered  may  be  determined  by 
these  tensile  tests,  and  this  question  frequently  arises  in  building 
operations.  In  this  connection  there  has  lately  been  much  ques- 
tion concerning  the  suitability  of  rock  screenings  for  use  in  place 
of  sand. 


30 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


Art.  io.— Variations  of  Sands  in  Tensile  Tests. 

The  following  experiments,  reported  by  E.  S.  Wheeler  in 
the  Report  of  the  Chief  of  Engineers,  U.  S.  Army,  for  1894, 
page  2321,  bear  directly  upon  this  point.  Table  I.  shows  the 
mean  tensile  strength  attained  by  various  mixtures  of  natural 
sand,  of  the  standard  sand  used  for  testing  and  of  various  rock 
screenings  with  natural  cements;  each  result  shown  is  an  aver- 
age of  five  to  ten  specimens,  all  briquettes  being  one  cement 
to  three  sand.  The  sands  were  all  brought  to  the  same  degree 
of  fineness  by  sifting  and  remixing,  there  being  used,  in  all 
cases,  excepting  for  the  standard  sand,  25  per  cent,  each  of  sand 
retained  between  sieves  Nos.  20  to  30,  30  to  40,  40  to  50  and  50 
to  80.  The  superiority  of  the  mixtures  formed  from  screenings 
obtained  from  crushed  limestone  and  sandstone  is  clearly  shown. 
The  table  is  for  natural  cements  only;  but  Portland  cements  fur- 
nished exactly  similar  results. 

TABLE  I. 


Kind  of  Sand 

Mean  Tensile  Strength  in  Lbs.  Per  Square  Inch  at  Age  of 

28  Days 

6  Months 

1  Year 

2  Years 

117 
93 
162 
113 
118 

344 
297 
467 
316 
330 

356 
339 
526 
416 
342 

332 
308 
601 
462 
324 

Point  aux  Pins  Natural  Sand  . 
Limestone  Screenings  

The  same  experimenter  records  on  page  2806  of  the  Report  of 
the  Chief  of  Engineers,  U.  S.  Army,  for  1896,  experiments  made 
in  determining  the  tensile  resistance  of  briquettes  when  mixed 
with  natural  sand  of  varying  fineness.  The  sand  was  Point  aux 
Pins,  and  each  result  in  Table  II.  is  an  average  of  five  briquettes, 
the  briquettes  being  one  cement  to  two  sand.  Portland  cement 
was  used.  The  exponents  of  the  letters  C,  M,  F  and  V  show  the 
percentages  of  each  fineness  used,  C  being  the  material  passing 
the  No.  io  sieve,  V  passing  the  No.  40  sieve,  M  being  the  ma- 
terial retained  between  the  20  to  30  sieves,  and  F  between  the  30 
to  40  sieves.  The  results  obtained  are  very  interesting.  They 
show  that  the  mortar  in  which  the  sand  contains  the  greatest 


Art.  10.]          VARIATIONS  OF  SANDS  IN  TENSILE  TESTS. 


31 


variations  in  the  sizes  of  grain  attains  the  greatest  strength.  This 
is  in  perfect  accord  with  the  opinion  that  the  balancing  of  the 
material  in  a  mortar  is  of  the  utmost  importance. 


TABLE  II. 


Fineness 

Tensile  Strength  in  Pounds  per  Square  Inch  at  Age  of 

28  Days 

6  Months 

1  Year 

2  Years. 

M10   F° 
M4     F1 
M2     F4 
M1     F3 
M1     F2 

C5    M20 
C5     M20 
C°     M10 
C°     Ml0 
C5    M10 

yo 
V5 
V4 
y« 

V7 
p40     yss 

p35       y45 

pso     yso 
p25     yeo 

342 
300 
290 
246 
271 

471 
448 
425 
384 
366 

566 
544 
551 
528 
540 

560 
515 
494 
•  455 
456 

18  Months 

581 

592 
585 
589 
593 

591 
507 
503 
442 
438 
3  Years 
632 
622 
587 
629 
622 



Exponents  of  letters  C,  M,  F,  V  show  numbers  of  parts  of  each  degree  of  fineness  used;  C 
passes  No.  10  sieve;  M,  between  Nos.  20  to  30;  F,  between  Nos.  30  to  40;  V  passes  No.  40. 

Figure  i  is  taken  from  tests  reported  by  R.  Feret  in  the  "An- 
nales  des  Fonts  et  Chaussees,"  1892,  and  shows  the  ultimate  com- 
pressive  resistance  attained  by  various  mortars  mixed  with  vari- 


C    2840  Lbs. 
.      person. 


]     1420  Lbs. 

to      per  sq.  in. 


7 


^     Cement  .0 
B       Sand  1.0 


.2        .3         .4         .5        .6         .7         .8         .9       1.0 
.8        .7        .6         .5        .4        .3        .2         .1        .0 
Parts  of  Sand  and  Cement 


FIG.  1.— FERET'S  TESTS. 

ous  proportions  of  the  same  cement  to  two  kinds  of  sand,  the 
relations  varying  from  neat  to  1 19.  The  specimens  were  im- 
mersed two  months  in  sea  water,  and  two  kinds  of  sand  were 


32 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


used — one,  which  was  marked  "Q,"  was  very  coarse  sand;  the 
other,  marked  "P,"  very  fine.  It  will  be  seen  that  the  coarse 
sand  gave  uniformly  higher  resistance  than  the  fine. 

Table  III.  is  taken  from  a  paper  by  E.  S.  Larned,  presented 
before  the  American  Society  for  Testing  Materials,  1903,  and 
shows  the  tensile  strength  of  cement  mortar  with  sand  grains  of 
different  diameters.  Each  result  shown  is  an  average  of  six 
briquettes.  The  table  gives  only  the  results  for  Giant  Portland 
cement  mortar,  one  part  cement  to  two  of  sand  by  weight,  but  the 

TABLE  III. 


Percentage  of  Sand  Used 

Ultimate  Tensile  Strength  at  the  Age  of 

No.  30 

No.  20 

No.  100 

Fine 

7  Days 

28  Days 

6  Months 

100 







286 

288 

412 

_ 

100 





294 

331 

473 





100 



201 

226 

294 







100 

129 

159 

223 

80 

10 

10 



361 

380 

486 

70 

15 

I3# 

2^ 

301 

303 

428 

60 

20 

15 

5 

307 

311 

419 

50 

25 

17# 

7/2 

391 

400 

538 

40 

30 

20 

10 

350 

355 

475 

30 

25 

30 

15 

362 

359 

478 

20 

20 

40 

20 

317 

374 

480 

10 

15 

50 

25 

291 

354 

488 

50 





50 

247 

287 

351 

50 

50 





440 

408 

542 

50 



50 



309 

336 

438 

25 

25 

25 

25 

279 

337 

447 

Crushed 

Quartz 

3  Months 

40 



60 



257 

331 

351 

Natural  sand  used  :  first  passed  through  No.  8  screen  and  residue  excluded  ;  No.  30  sand 
passed  No.  20  screen  and  caught  on  No.  30  screen;  No.  20  sand  passed  No.  8  screen  and 
caught  on  No.  20  screen  ;  No.  100  sand  passed  No.  30  screen  and  caught  on  No.  100  screen. 
Fine  is  clean  white  sand  sifted  through  No.  100  screen. 

original  paper  shows  similar  results  with  tests  upon  two  natural 
cements.  All  the  briquettes  were  gauged  with  the  same  per- 
centage of  water.  It  will  again  be  noticed  that  those  briquettes 
in  which  the  sand  is  composed  of  varying  percentages  of  the  dif- 
ferent kinds  show  uniformly  greater  strength  than  those  bri- 
quettes formed  of  one  kind  of  sand  only.  In  those  briquettes  in 
which  one  grade  of  fineness  of  sand  only  is  used  the  coarsest 
sand  shows  the  highest  ultimate  strength. 


Art.  10.]         VARIATIONS  OF  SANDS  IN  TENSILE  TESTS. 


33 


R.  Feret  records,  in  the  "Annales  des  Fonts  et  Chaussees," 
1892,  a  series  of  tensile  tests  on  1 13  mortar  in  which  the  cements, 
in  all  cases,  were  the  same,  but  the  sand  was  composed  of  many 
different  materials.  These  materials  were  used  either  neat  with 
the  cement  or  in  combination  with  each  other.  Among  the  ma- 
terials were  porphyry,  granite,  marble,  chalk,  quartzite,  broken 
glass,  crushed  brick,  charcoal,  sawdust,  mica,  etc.  All  speci- 
mens were  treated  exactly  alike  and  were  kept  in  sea  water  for 
various  periods  of  time  up  to  one  year.  Of  all  these  materials, 
it  was  found,  at  the  end  of  a  year,  that  the  1 13  marble  mortar 
gave  the  highest  ultimate  tensile  resistance,  and  that  the  granite, 
quartz  and  mica  mixtures  furnished  values  considerably  less. 
The  actual  values  obtained  by  these  mixtures  are  not  of  much 
importance;  but  it  is  interesting  to  record  Feret's  results  on 
marble,  since  they  substantiate  the  claim  that  a  calcareous  stone 
yields  stronger  concretes  than  a  quartz  or  granite  stone. 

TABLE    IV. 


Material 

Proportion  of  Sand 
to  Cement  by 
Volume 

Ult.  Tensile  Resistance  in  Lbs.  per  Sq.  In. 
at  the  Age  of 

1   Day 

7  Days 

28  Days' 

2:1 
2:1 
2:1 
3:1 
3:1 
3:1 

107 
92 
86 
37 
39 
29 

364 
330 
175 
228 
223 
122 

530 

528 

311 
394 

Fine  Screenings.  
Sand  from  Reservoir.  . 

Pine  Screenings    

Sand  from  Reservoir.  .  . 

In  connection  with  this  it  is  of  interest  to  note  that  in  "Engi- 
neering News,"  May  17,  1890,  is  given  an  abstract  of  results  ob- 
tained by  breaking  a  large  number  of  cement  blocks  3  feet  3^ 
inches  long  and  7.9  inches  square,  the  original  tests  having  been 
recorded  in  "Wochenschrift  des  Oester.  Ing.  Ver."  Sufficient  de- 
tails are  not  provided  to  permit  an  analysis  of  the  results  as  flex- 
ure tests,  but  the  following  general  statement  is  worth  recording: 
That  the  strength  of  specimens  made  with  granite,  with  clinkers 
(vitrified  brick)  and  with  sandstone  varied  in  the  order  named, 
granite  showing  the  greatest  strength. 

Table  IV.  is  taken  from  a  report  made  by  Mr.  A.  Black,  of 
the  Department  of  Civil  Engineering  of  Columbia  University,  to 


34 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


the  Investigating  Commission  on  the  Jerome  Park  Reservoir, 
1903,  and  shows  the  tensile  strength  of  three  kinds  of  mortars 
mixed  with  Atlas  Portland  cement.  The  sand  for  these  mix- 
tures was  either  natural  Cow  Bay  sand,  or  the  natural  sand 
from  the  site  of  the  Jerome  Park  Reservoir,  or  artificial  sand 
composed  of  rock  screenings.  Each  figure  is  the  average  of  a 
large  number  of  briquettes,  and  it  is  seen  that  the  briquettes 
made  with  the  screenings  are  not  inferior  to  those  briquettes 
made  from  the  natural  sand. 

Table  V.  shows  the  relative  strength  of  sand  and  stone  dust 
mortars,  as  determined  by  T.  S.  Clarke,  and  as  reported  by  him 
in  the  "Engineering  News"  of  July  24,  1902.  In  his  case,  how- 
ever, the  stone  dust  was  very  much  finer  than  the  sand,  and  the 

TABLE  V. 

Showing  Strength  of  Sand  Mortar  Compared  with  Stone  Dust  Mortar; 
Portland  Cement;  24  Hours  in  Air,  6  Days  in  Water;  Amount  of 
Water  Used,  io%- 


Proportions 

Av'ge  Tensile  Strength, 
Lbs.  per  Sq.  In. 

Average  Number 
of  Tests 

Cement 

Sand 

Stone  Dust 

! 

— 

2 

245 

15 

I 

1 

— 

345 

16 

I 

— 

3 

216 

3 

I 

3 

— 

241 

3 

results  show  that  the  tensile  strength  of  the  natural  sand  mortar 
is  greater  than  that  of  the  stone  dust  mortar.  This  is  to  be  ex- 
pected, if  the  fineness  of  the  two  varieties  exhibits  the  difference 
noted. 

Reviewing  the  preceding  experiments,  it  may  be  concluded 
that  rock  screenings  may  be  substituted  for  sand,  either  in  mor- 
tar or  concrete,  without  any  loss  of  strength  resulting.  This  is 
important  commercially,  for  it  precludes  the  necessity  of  screen- 
ing the  dust  from  crushed  rock  and  avoids,  at  the  same  time,  the 
cost  of  procuring  a  natural  sand  to  take  its  place. 

Effect  of  Clay  in  Sand — In  construction  work  the  question  of 
the  presence  of  fine  clay  in  a  natural  sand  is  generally  at  once  dis- 
posed of  by  prohibiting  it,  but  the  following  data  show  that  this 
solution  is  not  satisfactory. 


Art.  10.] 


EFFECT  OF  CLAY  IN  SAND. 


35 


Table  VI.  is  taken  from  Vol.  XIV.  of  the  Transactions  of  the 
American  Society  of  Civil  Engineers,  1885,  m  which  are  re- 
corded experiments  made  by  E.  C.  Clarke  concerning  the  adul- 
teration of  sand  with  clay.  It  will  be  seen  that  mixtures  of  clay 
and  cement  without  the  addition  of  sand  have  no  permanent 
strength :  but  the  presence  of  clay  in  moderate  amounts  does  not 
weaken  cement  mixtures.  Each  figure  in  the  table  represents 
the  average  ultimate  tensile  resistance  in  pounds  per  square  inch 
of  fifteen  briquettes-made  from  Portland  cement,  but  experiments 
made  with  the  natural  cements  furnished  similar  results. 

G.  J.  Griesenauer  has  reported  in  ''Engineering  News,"  April 
28,  1904,  tests  made  on  the  tensile  strength  of  Portland  and 
natural  cement  mixtures  when  the  sand  which  was  used  con- 
tained various  percentages  of  clay  or  loam;  also,  when  the  sand 
was  natural  dirty  sand,  just  as  it  came  from  the  sand  bank,  and 

TABLE  VI. 


Age 

Cement  2 
Clay  1 

Cement  1 
Clay  1 

Cement  1 
Sand  2 

Cement  1 
Sand  2 
Clay  0.2 

Cement  1 
Sand  2 
Clay  0.4 

Cement  1 
Sand  2 
Clay  0.6 

I  Week  

185 

192 

150 

197 

185 

145 

I  Month  
6  Months  
I  Year  

263 
248 
303 

271 
322 
301 

186 
320 
340 

253 
361 
367 

245 
368 
401 

203 
317 
384 

when  the  same  was  washed.  The  experiments  extended  over  a 
considerable  period  of  time. 

Two  sets  of  experiments  (which  it  is  unnecessary  to  repro- 
duce here)  were  made  on  Portland  cement  mortars  i  :2  and  1 13,  in 
which  loam  was  added  to  the  clean  sand  in  percentages  as  high 
even  as  20  per  cent.  The  results  from  those  tests  show  that  the 
clay  affected,  in  almost  all  cases,  the  1:2  mortars  adversely,  but 
appeared,  on  the  contrary,  to  benefit  the  I  :$  mixtures  for  almost 
every  percentage  of  loam  added  and  for  all  ages.  These  con- 
tradictory results  are  probably  explained  by  the  fact  that  in  the 
one  case  the  loam  helped  to  balance  the  mixture,  and  in  the  other 
case  not. 

Figures  2  and  3,  from  the  same  tests,  are,  however,  of  greater 
interest,  since  they  represent  more  nearly  conditions  in  practice. 
Figure  2  shows  the  strength  of  1:3  Portland  cement  mortars 


36 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


mixed  with  natural  sand  taken  from  various  pits  and  containing 
the  percentages  of  loam  indicated.  Figure  3  shows  the  results 
obtained  on  1 13  mortars  in  which  the  sand  containing  6  per  cent, 
of  loam  was  first  used  in  its  natural  condition  and  then  after  hav- 
ing been  washed. 

The  results   are   entirely   harmonious.     They   show   that   the 
presence  of  loam  in  a  1:3  mortar  rarely  decreases  the  ultimate 


Tests  of  1-3  Mortar  with  Sand 
from  Different  Pits 

FIG.  2.— TESTS    BY   GRIESENAUER. 

strength.  As  has  already  been  said,  the  reason  for  this  is  prob- 
ably to  be  explained  by  the  better  balancing  of  the  mixture. 
Nothing  indicates  why  this  same  reasoning  may  not  apply  as 
well  to  mixtures  of  cement,  sand  and  stone.  If  this  be  the  case, 
there  is  no  reason  why  a  loamy  sand  should  not  be  used  for 
making  concrete. 

Professor  C.  E.  Sherman  has  also  recorded  in  the  "Engineer- 
ing News"  of  November  19,  1903,  an  extended  series  of  tests 
which  he  had  made  concerning  the  effect  of  clay  and  loam  on 
cement  mortars.  The  tests  were  made  on  the  usual  form  of  ten- 


Art.  10] 


EFFECT  OF  CLAY  IN  SAND. 


37 


sile  briquette,  with  three  different  kinds  of  sand,  lake,  bank  and 
crushed  quartz,  each  of  which  was  artificially  mixed  with  varying 
percentages  of  clay  and  loam  up  to  15  per  cent.  Five  specimens 
of  every  mixture,  and  with  two  different  brands  of  Portland 
cement,  were  tested  at  ages  varying  between  one  week  and  one 
year.  The  uniformity  of  the  results  is  such  that  it  seems  un- 
necessary to  give  in  detail  any  of  the  experiments,  since  only 
five  curves  out  of  seventy-two,  representing  the  tensile  strength 


400 


200 


150 


100 


(kLtam 


-V£ 


Sand 


»tf»B^ 


Tests  of  1:3  Mortar  with  6%Loamy  San.d 

and  with  game  Sand  Washed 
FIG.  3.-TESTS   BY   GRIESENAUER. 

of  a  mortar  composed  of  sand  with  clay  or  loam,  fell  below  the 
curves  representing  the  tensile  strength  of  the  clean  sand  mortar. 
And  in  eight  cases  out  of  twelve  the  15  per  cent,  mixtures  fur- 
nished the  very  highest  results  at  the  end  of  one  year. 

Table  VII.  shows  results  abstracted  by  the  "Engineering 
Record,"  July  16,  1904,  from  tests  describel  by  Charles  M.  Mills 
in  a  paper  read  before  the  Philadelphia  Engineers'  Club.  The 
tests  were  made  in  the  laboratory  of  the  Philadelphia  Rapid 
Transit  Commission  on  briquettes  of  the  standard  tensile  form. 


38 


PHYSICAL  TESTS  OF  CEMENTS. 


[Ch.  II. 


The  gravel  used  in  the  mortar  tests  after  screening  fulfilled  the 
requirements  for  "coarse  sand  or  gravel,  graded  from  coarse  to 
fine,  to  reject  all  particles  exceeding  I  inch  in  diameter/'  but  it 
contained  a  considerable  quantity  of  loam.  Tests  were  made 
with  the  natural  gravel,  with  the  same  screened,  and  with  the 
same  washed,  as  fully  shown  in  the  table,  each  result  being  the 
average  of  4  to  6  specimens. 

The  greatest  strength  was  attained  in  the  crushed  rock  mix- 
tures, and  the  lowest  strength  was  given  by  the  standard  quartz 

TABLE  VII. 


Material 

Percent- 
age of 
Loam  in 
the  Sand 

Percent- 
age of 
Water 
Used  in 
Mixing 

Av.  Tensile  Strength 
in  Lbs.  per  Sq.  In. 

1  Day  in 
Air 
6  Days  in 
Water 

1  Day  in 
Air 
27  Days 
in  Water 

25 
3 
25.2 
3.2 
16.4 

11.4 

21 
9.9 

II.  2 
10.7 
13-7 
II.  2 
15.0 

12.5 
II.  2 

12.5 

527 
175 

208 
230 
219 
211 
213 

282 
279 

218 

862 
263 

316 
355 
335 
367 
385 

459 
416 

372 

I  Cement  to  3  Sand. 

I  Cement  to  3  Gravel. 

I  Cement  to  3  Gravel. 

I  Cement  to  3  Gravel. 

I  Cement  to  3  Gravel. 

18%  retained  on  Sieve  No.  20. 
I  Cement  to  3  Grit. 

HTrnn  Rorlc  firit 

I  Cement  to  3  Grit. 
J       Crushed  Trap  Rock  

I  Cement  to  3  Crushed  Rock. 
K—  Trap     Rock    Grit    and     Excavation  ) 
Gravel  (unwashed,  screened)  ) 
I  Cement,  \l/2  Grit,  1%  Gravel. 

sand;  these  results  might  have  been  expected.  In  groups  E  to 
F,  which  contained  the  loamy  gravel,  the  variation  due  to  the 
different  percentages  of  loam  is  seen  to  be  practically  negligible; 
a  very  slight  increase  is  shown  for  the  clean  gravel  specimens  at 
the  end  of  28  days.  In  the  work  for  which  these  tests  were  a 
preliminary,  a  mixture  of  equal  parts  of  crushed  trap  rock  grit 
and  screened  gravel  was  used. 


Art.  II.]  TEST  OF  CONSTANCY  OF  VOLUME.-  39 

It  appears,  therefore,  that  the  presence  of  a  loam  or  clay  in  a 
sand  may  not  be  objectionable. 

Art.  n. — Test  of  Constancy  of  Volume. 

Improperly  made  cements  sometimes  fail,  even  after  a  con- 
siderable period  following  the  setting,  by  the  checking  or  swell- 
ing of  the  cement,  which  in  turn  causes  disintegration  of  the  mor- 
tar. The  object  of  the  test  of  constancy  of  volume,  therefore,  is 
to  endeavor  to  determine  such  qualities,  if  present,  in  as  short  a 
time  as  possible. 

The  tests  are  made  on  small  pats  of  cement,  which  may  be 
treated  in  various  ways,  such  as  by  immersion  in  hot  water  or  in 
cold  water  or  in  chemical  solutions;  after  a  certain  lapse  of  time 
they  are  then  examined  as  to  the  presence  of  defects,  such  as 
distortion  of  the  specimen  or  cracks.  The  hot  water  or  chemical 
test,  however,  has  never  been  considered  entirely  satisfactory, 
either  for  the  purpose  of  accepting  or  rejecting  a  cement.  The 
failure  to  pass  the  hot  water  test  does  not  necessarily  imply  re- 
jection; it  classes  a  cement  as  suspicious,  but  the  appearance  of 
defects  in  specimens  left  in  cold  water  for  periods  of  seven  to 
fourteen  days  does  determine  its  unfitness  for  use. 

It  is  proper  to  say,  however,  that  sometimes  freshly  burned 
cements,  which  fail  to  pass  the  "cold  water"  test,  may  pass  the 
same  after  some  period  of  "aging";  it  is  therefore  possible  that 
the  same  cement  may  be  accepted  at  a  later  period  after  having 
been  previously  rejected.  Quantitative  results  are  not  obtained 
in  these  tests. 


CHAPTER  III. 
GENERAL  PHYSICAL  PROPERTIES. 

Before  treating  of  the  resistance  to  stress  of  cement  mixtures 
the  following  physical  properties  will  be  considered: 

(a)  The  change  in  volume  of  cement  mixtures  when  setting. 

(b)  The  coefficient  of  expansion  due  to  temperature  changes. 

(c)  The  action  of  sea  water. 

(d)  The  porosity  and  impermeability  of  cement  mixtures. 

(e)  The  effect  of  freezing. 

(f)  The  adhesion  of  iron  rods  to  cement  mixtures, 
'(g)  The  fatigue  of  cement  mixtures. 

Art.  12 — Variation  in  Volume  of  Cement  Mortars 
in  Air  and  Water. 

The  general  conclusions  as  to  the  variation  of  volume  which 
takes  place  during  the  hardening  of  cement  mixtures  are  prac- 
tically agreed  upon  by  all  experimenters;  they  have  been  well 
stated  by  Professor  G.  F.  Swain,  who  made  elaborate  experiments 
upon  the  changes  of  dimensions  during  the  setting  of  American 
cements  at  the  Massachusetts  Institute  of  Technology  with  the 
aid  of  two  students.  These  tests  are  reported  in  the  Trans- 
actions of  the  American  Society  of  Civil  Engineers  for  July, 
1887.  Experiments  were  made  upon  several  brands  of  natural 
and  of  Portland  cement.  Five-inch  cubes  were  made,  both  of 
neat  cement  and  with  a  mixture  of  one  cement  to  one  sand.  In 
two  cases  mixtures  of  one  cement  and  three  sand  were  also 
made.  One  specimen  of  each  pair  of  cubes  was  left  in  the  air, 
the  other  in  water.  Observations  were  taken  at  intervals  rang- 
ing from  one  day  to  twelve  weeks,  and  the  following  conclusions 
were  reached: 


Art.  12.]        VARIATION  IN  VOLUME  IN  AIR  AND  WATER.  4 1 

1.  Cement  mixtures  hardening  in  air  diminish  in  linear  dimen- 
sions, at  least  to  the  end  of  twelve  weeks,  and  in  most  cases  pro- 
gressively. 

2.  Cement  mixtures  hardening  in  water  increase  in  like  man- 
ner, but  to  a  less  degree. 

3.  The  contractions  and  expansions  are  greatest  in  neat  cement 
mortars. 

4.  In  general  the  quick  setting  cements  show  the  greatest  con- 
traction when  neat,  and  the  expansion  of  the  quick  setting  ce- 
ments is  also  greater. 

5.  The  changes  are  less  in  mortars  containing  sand. 

6.  The  changes  are  less  in  water  than  in  air. 

7.  The  contraction,  at  the  end  of  twelve  weeks,  is 

For  neat  cement 0.14%  to  0.32% 

For  one  cement  to  one  sand.  .   0.08%  to  0.17% 

8.  The  expansion,  at  the  end  of  twelve  weeks,  is 

For  neat  cement.  . . 0.04%  to  0.25% 

For  one  cement  to  one  sand.  .   0.00%  to 0.08% 

9.  The  contraction  or  expansion  is  essentially  the  same  in  all 
directions. 

Professor  Bauschinger  of  Munich  reported  the  results  of  simi- 
lar tests  in  "Mittheilungen  aus  dem  Mechanisch-Technischen 
Laboratorium"  of  the  Royal  Technical  Institute  of  Munich,  Vol. 
VII.,  and  his  results  confirm  those  of  Professor  Swain;  his  test 
specimens  were  cubes  4.72  inches  on  a  side.  The  following  table 
shows  his  result : 

TABLE  I. 


Mixture 
Cement  to  Sand 

Age 

Contraction  in  Per  Cent. 
Hardening  in  Air 

Expansion  in  Per  Cent. 
Hardening  Under  Water 

Neat 
1:3 
1:5 

16  weeks 
16  weeks 
16  weeks 

.12  to  .34 
.08  to  .15 
.08  to  .14 

.01  to  .15 
0  to  .02 
—0.03  to  .02 

Similarly  Mr.  John  Grant  records  in  Vol.  LXIL,  Proc.  Inst. 
Civ.  Eng.,  the  results  of  his  experiments  on  prisms  four  inches 
long  and  two  inches  square,  hardening  only  in  water.  He  finds 
that  at  the  end  of  a  year  neat  cements,  without  plaster  of  Paris, 


42 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


expand  .09  to  .21  of  I  per  cent.,  and  for  one  cement  to  three  sand 
.01  to  .06  of  i  per  cent.  These  figures  were  increased  for  ce- 
ments with  gypsum. 

Dr.  C.  Schumann,  in  his  book,  "Portland  Cement,"  1899,  re-- 
cords the  results  obtained  by  him  in  measuring  the  increase  in 
volume  for  specimens  3.9  inches  long  with  a  cross-section  of 
•775  sq.  in.,  which  were  immersed  in  water  for  various  periods 
of  time.  Table  II.  is  abstracted  from  page  78  of  this  book;  each 
value  shown  gives  the  average  percentage  of  increase  in  length 
for  ten  specimens  of  each  kind: 

TABLE  II. 


'Age  in  Weeks 

Neat  Specimen 

1   Cement 
3  Normal  Sand 

I 

048$> 

015 

4    •    • 

082 

021 

13    ... 

104 

024 

26  

125 

028 

39  

139 

030 

52  

146 

O"^ 

M.  Gary  records  in  the  Trans.  Am.  Soc.  Civ.  Eng.  for  October, 
1893,  the  results  of  some  tests  by  Dr.  Tornei,  manager  of  the 
Stern  Portland  cement  factory;  the  size  of  specimen  was  the 
same  as  used  by  Bauschinger.  Table  III.  is  an  abstract,  being 
the  average  of  the  first  six  cements  there  shown. 

TABLE  III. 


Mixture 

Age  in  Days 

Percentage  of  Contraction, 
Hardening  in  Air 

Percentage  of  Expansion, 
Hardening  Under  Water 

r 

7 

.064 

.014 

Neat    < 

28 

129 

026 

90 

.181 

.021 

I  Cement  \ 
3  Sand..  /  "    '1 

7 
28 
90 

.018 
.053 
.089 

.Oil 
.018 
.028 

Considere  has  stated  that  the  shrinkage  of  cement  in  air  may 
vary  from  0.15  to  0.2  per  cent,  for  neat  cement,  and  from  0.03  to 
0.05  per  cent,  for  mortar  poor  in  cement;  and,  similarly,  he  has 
found  that  pure  cement  swells  under  water  from  o.i  to  0.2  per 
cent.,  and  that  concrete  poor  in  cement  swells  from  0.02  to  0.05 


Art.  I3-]  THERMAL  LINEAR  EXPANSION.  43 

per  cent.  These  figures  show  accordance  with  the  preceding  re- 
sults and  may  be  adopted  for  use. 

The  report  of  the  Boston  Transit  Commission  for  the  year 
ending  August  15,  1901,  records  some  measurements  made  by 
H.  S.  R.  McCurdy  on  the  shrinkage  taking  place  in  concrete 
after  it  has  set.  Two  beams  were  used;  the  one  kept  in  air  was 
8  inches  square  and  8.9  feet  long,  and  the  other,  whose  size  is 
not  given,  was  kept  in  water.  The  conclusions  reached  were 
that  the  concrete  hardened  in  air  would  shrink  .028  per  cent,  in 
twelve  weeks,  and  that  the  concrete  in  water  would  shrink  two- 
thirds  of  this. 

The  latter  conclusion  does  not  agree  with  results  obtained  by 
other  experimenters,  and  probably  little  reliance  should  be  placed 
upon  these  figures,  since  the  apparatus  used  was  crude  and  the 
number  of  tests  was  small. 

Art.  13 — The  Coefficient  of  Expansion  Due  to 
Temperature  Changes. 

The  earliest  work  recorded  concerning  the  linear  thermic  ex- 
pansion of  concrete  is  due  to  Bouniceau,  who  published  his  re- 
sults in  the  "Annales  des  Fonts  et  Chaussees,"  1863,  page  178. 
His  work  was  performed  on  rectangular  prisms  65  to  94  inches 
long  and  about  7  inches  on  each  side,  the  blocks  being  placed  in 
water  whose  temperature  varied  from  10  to  95  degrees  C.  The 
apparatus  used  was  checked  by  measuring  the  determined  co- 
efficient of  expansion  for  other  materials. 

Bouniceau  tested  altogether  ten  blocks,  either  of  solid  stone, 
concrete,  mortar  or  neat  cement,  the  latter  being  in  all  cases 
Portland;  the  following  are  the  results  obtained  on  the  cement 
mixtures: 

Neat  Portland  cement 00000594  per  degree  F. 

One  cement  to  two  silicious  sand 00000655    "        "        " 

Concrete  (proportions  not  given)  (stone 

being  silicious  gravel) 00000795    "        "        " 

Professor  W.  D.  Pence  of  Purdue  University  has  made  a 
series  of  investigations,  the  results  of  which  are  given  in  a  paper 
of  the  Western  Society  of  Engineers,  November,  1901.  He 


44 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


made  experiments  on  Portland  cement  concretes  of  the  composi- 
tions shown  in  the  following  table.  The  values  there  given  show 
the  coefficient  of  linear  expansion  per  degree  Fahrenheit. 

TABLE  I. 


Kind  of  Concrete 

Coefficient  of  Expansion 

I  Cement  

..  ^ 

2  Sand 

I 

0000055 

I 

.      \ 

2  Sand            

.  ( 

.0000054 

4  Gravel  

J 

.  | 

} 

.0000053 

The  method  of  conducting  these  experiments  involved  the 
comparison  of  the  concrete  bars  with  metal  bars,  and  the  results 
obtained  may  perhaps  be  regarded  with  some  suspicion  on  this 
account.  Busing  and  Schumann,  in  "Portland  Cement,"  page 
77,  quote  Meier  as  giving  the  coefficient  of  expansion  of  neat 
cement  between  — 5  to  -f-25  degrees  C.  as  being  the  same  as  for 
iron.  Similarly,  Christophe,  in  "Le  Beton  Arme,"  page  706, 
quotes  Bouniceau,  Meier,  Bauschinger,  Adie  and  Durand-Claye 
in  stating  that  the  coefficient  may  vary  from  .00000667  to 
.00000805  per  degree  F.,  and  that  it  is  essentially  constant  even 
with  varying  percentages  of  mixture. 

Berger  and  Guillerme,  in  "Ciment  Arme,"  page  84,  quote 
Durand-Claye  as  giving  the  coefficient  of  expansion  but  little 
different  from  .0000075  per  degree  F. 

In  the  early  part  of  1902  tests  were  made  by  Messrs.  J.  G.  Rae 
and  R.  E.  Dougherty,  graduating  students  in  Civil  Engineering 
at  Columbia  University,  on  one  bar  of  1:3:5  gravel  Portland  ce- 
ment concrete  and  one  1 :2  mortar  bar,  the  bars  being  four  inches 
by  four  inches  in  cross-section  and  about  three  feet  long,  with 
an  age  of  about  five  and  one-half  years. 

The  results  found  are  as  follows : 


Mixture 

Coefficient  of  Expansion  per  Degree  Fahrenheit 

1:3:5 
1:2 

.00000655 
.00000561 

Art.  14.]         THE  ACTION  OF  SEA  WATER  ON  CEMENTS.  45 

The  tests  were  made  under  the  direction  of  Professor  W.  Hal- 
lock  of  the  Department  of  Physics  of  Columbia  University,  and 
the  results  are  believed  to  be  accurate. 

It  appears  therefore  that  the  thermal  linear  expansion  of  ce- 
ment mixtures  does  not  differ  materially  from  that  of  iron. 


Art.  14. — The  Action  of  Sea  Water  on  Cements. 

The  prevention  of  the  disintegration  of  cement  mixtures  by 
sea  water  or  by  water  containing  solutions  of  salts  has  long  been 
a  question  of  dispute  among  chemists,  although  the  reasons  for 
its  occurrence  are  fairly  established.  Sea  water  contains  small 
percentages  of  magnesium-sulphate  and  magnesium-chloride,  in 
addition  to  the  ordinary  salt,  sodium  chloride.  The  magnesium- 
sulphate  and  magnesium-chloride  react  either  on  the  hardened 
cement  or  on  the  hydrated  lime  which  is  present  in  the  cement 
and  form  calcium-sulphate  and  calcium-chloride.  The  calcium- 
sulphate  crystallizes  and  expands,  and  therefore  disintegrates  the 
mass,  but  the  .calcium-chloride  is  soluble  and  simply  deposits 
inert  magnesia. 

Dr.  Michaelis  believes  that  this  chemical  action  can  be  an- 
nulled by  adding  to  the  cement  some  pozzalana,  which,  in  com- 
bination with  lime,  has  of  itself  the  property  of  hardening  under 
water.  The  lime  which  is  needed  must  separate  from  the  cement, 
since  pozzalana  does  not  harden  by  itself.  Candlot  and  others 
think,  however,  that  the  difficulty  is  more  easily  solved  by  mak- 
ing the  cement  mixture  impermeable  to  the  water,  and  that,  in 
order  to  avoid  disintegration,  it  is  simply  necessary  to  prevent 
the  sea  water  from  attacking  the  interior  of  the  mass.  They  be- 
lieve, then,  that  if  the  addition  of  pozzalana  is  of  value,  it  is  only 
so  because  it  provides  a  denser  mixture. 

Le  Chatelier  has  formulated  a  new  opinion  on  this  question 
and  attributes  the  disintegration,  in  large  manner,  to  the  pres- 
ence of  alumina.  In  that  case  the  sulphates  in  the  water  attack 
the  aluminate  of  lime  and  form  sulpho-aluminate  of. lime,  which 
swells  and  expands.  Under  those  conditions  Le  Chatelier  con- 
siders it  advantageous  to  have  as  little  alumina  as  possible  in  the 


46  GENERAL  PHYSICAL  PROPERTIES.  [Ch.  III. 

cement,  or  to  replace  it  as  far  as  possible  by  iron  oxides.  No  ex- 
tended tests  have  as  yet  been  applied  to  this  theory. 

A  complete  discussion  concerning  the  first  two  opinions  may 
be  found  in  Vol.  XXXVII.  of  the  Transactions  of  the  American 
Society  of  Civil  Engineers,  including  also  a  final  statement  of 
the  Association  of  German  Portland  Cement  Manufacturers  upon 
the  proposition  of  Dr.  Michaelis.  In  this  particular  instance  it 
is  declared  that  cement  mixtures  for  use  in  sea  water  are  not  im- 
proved by  the  addition  of  pozzalana  or  trass. 

R.  Feret  has  presented  a  paper,  in  Vol.  IV.,  1901,  of  the  "An- 
nales  des  Fonts  et  Chaussees,"  concerning  the  effect  of  the  addi- 
tion of  pozzalana  to  Portland  cements  which  are  to  be  used  in 
sea  water.  In  the  paper  are  recorded  tests  made  upon  several 
specially  manufactured  cements,  marked  G,  R,  T  and  A,  which 
were  afterward  used  in  actual  construction  work  in  harbors.  The 
G  cements  consisted  of  equal  weights  of  good  Portland  cement 
and  of  lightly  burned  gaize*;  the  R  cements  consisted  of  equal 
weights  of  good  Portland  cement  and  Roman  pozzalana;  the  T 
cements,  of  equal  weights  of  good  Portland  cement  and  trass, 
and  the  A  cements  were  manufactured  from  pastes  containing 
about  23  per  cent,  of  clay.  The  results  obtained  from  these  ce- 
ments were  compared  to  Portland  cements  of  various  brands, 
manufactured  from  a  paste  containing  about  21  per  cent,  of  clay. 
Tests  were  made  in  the  waters  of  the  harbors  of  Boulogne,  Calais, 
Havre,  La  Rochelle  and  Bordeaux.  The  longest  tests  extended 
over  a  period  of  three  and  one-half  years;  and  although  the  re- 
sults obtained  were  not  in  all  respects  harmonious,  it  was  found 
that  the  mortars  made  of  the  specially  prepared  cements  were,  in 
general,  stronger  and  showed  less  signs  of  disintegration  than 
the  mortars  made  from  the  ordinary  Portland  cements.  This 
was  found  to  hold  true,  however,  only  when  the  mixtures  were 
deposited  under  water.  When  the  mixtures  were  allowed  to 
harden  in  air  it  was  found  that  the  specially  prepared  cements 
possessed  little  strength,  even  after  an  interval  of  two  years.  The 
ordinary  cements  naturally  attained  their  usual  strength.  Feret 


*Gaize — A  light,  porous  stone  of  variable  degree  of  hardness,  resulting  from  the  silification 
of  certain  clays. 


Art.  14.]         THE  ACTION  OF  SEA  WATER  ON  CEMENTS. 


47 


finally  concludes  that  the  most  useful  mixture,  as  well  as  the 
most  economic,  is  made  by  grinding  together  two  parts,  by 
weight,  of  Portland  cement  to  one  of  gaize.  Such  a  cement  has. 
been  specially  made,  and  is  now  being  subjected  to  tests  in  the 
harbors  of  Bordeaux  and  Boulogne. 

There  are  two  ways  of  depositing  concrete  in  sea  water- 
either  as  blocks,  which  have  already  set  in  air,  or  by  depositing 
the  plastic  concrete,  by  means  of  buckets,  under  the  water. 
These  two  methods  admit  still  of  two  other  variations.  Concrete 
may  be  mixed  either  with  fresh  water  or  with  salt  or  brackish 
water.  There  is  at  present  a  lack  of  reliable  'information  as  to 
the  final  resistance  of  concrete  prepared  in  any  of  these  ways, 
although  the  question  is  being  studied  with  great  care  by  the  So- 
ciety of  German  Portland  Cement  Manufacturers,  who  estab- 

TABLE  I. 


Mixture 

Ratio  in  Percentages  of  Tensile  Strength  of  Sea 
Water  vs.  Fresh  Water  Hardening 

Age  in  Weeks 

1 

4 

26 

52 

104 

I  Cement, 
I  Cement, 
I  Cement, 
I  Cement, 
I  Cement, 

I  Sand  

92.0 
89.3 
92.6 
99.4 
91.5 

93.7 
92.2 
92.7 
88.8 
67.7 

93.3 

90.0 
77.5 
87.1 
76.3 

89.6 
90.5 
78.6 
74.3 
77.6 

92.6 

88.2 
80.5 
87.7 
74.0 

2  Sand  
4  Sand  

4  Sand,  ^  HydratLime. 
I  Sand,  l/2  HydratLime. 

lished,  in  1894,  with  the  aid  of  the  Prussian  government,  an  ex- 
periment station  on  the  island  of  Sylt,  in  the  North  Sea.  It  is 
there  also  that  it  is  proposed  to  determine  finally  the  soundness 
of  the  theory  advanced  by  Dr.  Michaelis  concerning  the  admix- 
ture of  pozzalana  in  concrete  which  is  to  remain  in  sea  water. 

Strength  in  Sea  Water — The  strength  of  cement  mixtures  does 
not  increase  as  rapidly  in  salt  water  as  in  fresh.  Experiments 
set  forth  by  Dyckerhoff  in  the  Proceedings  of  the  Association  of 
German  Portland  Cement  Manufacturers,  1896,  are  shown  in 
Table  I.,  in  which  are  given  the  ratios  in  percentages  of  tensile 
strengths  of  mortars  hardening  in  salt  and  fresh  water.  The 
table  shows  some  irregularities  in  regard  to  the  mixtures  includ- 
ing lime,  the  older  mixtures  of  which,  although  furnishing  high 


48 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


resistance  at  the  time  of  setting,  also  showed  marked  signs  of 
disintegration. 

Table  II.  furnishes  very  similar  results,  and  is  taken  from 
Busing  and  Schumann's  "Portland  Cements,"  page  128,  from 
experiments  made  by  Sympher  on  the  crushing  resistance  of 
mortars  when  deposited  in  weak  sea  water.  The  relations  be- 
tween results  of  the  fresh  and  sea  water  specimens  is  very  satis- 
factory, although  in  the  last  case  shown  the  specimens  were  at- 
tacked and  partially  destroyed  in  the  sea  water. 

Table  III.  is  taken  from  the  Report  of  the  Boston  Transit 
Commission  for  the  year  ending  June  30,  1902,  and  shows  the 
effect  of  keeping  briquettes  in  compressed  air,  in  fresh  water  and 

TABLE  II. 


Mixture 

Hardening  in 

Ultimate  Crushing  Resistance  in  Lbs.  per  Sq.  In. 
at  the  Age  of 

4 
Weeks 

52 
Weeks 

104 
Weeks 

Remarks 

I  Cement,  I  Sand.  .  •< 

'  \ 
I  Cement,  3  Sand.  .  / 
%  Hydrat  Lime  , 
I  Cement,  4  Sand.  .  f 
Yz  Hydrat  Lime.  .  .  -  \ 

FreshWater. 

Sea  Water.  .  . 

FreshWater'. 
Sea  Water.  .  . 
!  Fresh  Water. 
Sea  Water.  .  . 

4230 
3440 
3640 
3530 
2840 
2340 
2210 
2110 

6330 
4340 
5000 
4320 
3560 
3400 
2640 
2340 

6880 
5420 
5300 
4590 
4190 
3820 
2880 
2340 

Edges  broken  off;  disin- 
tegration in  sea  water 

in  sea  water.  The  briquettes  were  of  the  usual  type  used  in 
tensile  testing,  the  mixture  used  being  i  part  of  cement,  2,\  parts 
of  fine  crushed  stone,  ranging  in  size  from  an  impalpable  powder 
to  -J  inch  in  diameter,  and  4  parts  of  coarse  crushed  stone,  J  to  i 
inch  in  size.  All  the  briquettes  were  kept  in  air  at  60  to  80  de- 
grees Fahr.  for  the  first  twenty-four  hours  after  making,  and 
then  in  compressed  air  at  a  pressure  of  18  to  25  pounds  per 
square  inch  for  thirteen  days;  they  were  then  divided  into  three 
lots  and  placed  as  shown  in  the  table.  Each  figure  is  a  mean  of 
three  briquettes.  The  results  shown  belong  to  Vulcanite  cement 
only,  but  other  brands  acted  similarly. 

It  will  be  seen  that  the  briquettes  kept  in  compressed  air  were 
always  the  strongest,  and  that  up  to  the  age  of  four  months  there 
was  no  practical  difference  between  those  kept  in  fresh  water  and 


Art.  14.]         THE  ACTION  OF  SEA  WATER  ON  CEMENTS. 


49 


in  sea  water ;  but  at  nine  months  the  sea  water  briquettes  did  de- 
preciate considerably  in  strength. 

R.  Feret  has  recorded  in  Vol.  CVII.  of  the  Proceedings  of  the 
Institution  of  Civil  Engineers,  page  163,  some  very  interesting 


TABLE   III. 


Place  of  Keeping  the  Briquettes 

Average  Tensile  Strength  in  Lbs.  per 
Square  Inch  at 

1  Month 

4  Months 

9  Months 

Compressed  Air  (18-25  Pounds  Pressure). 
Fresh  Water  (Changed  Each  Day)  

440 
460 
420 

617 

501 

533 

866 
662 
543 

Sea  Water  (Under  the  Harbor)    

experiments  on  the  hardening  of  cement  mortars  in  fresh  and  sea 
water.  Table  IV.  is  an  abstract  of  these  tests.  Each  result 
shown  is  a  mean  of  six  tensile  briquettes  of  .775  square  inch 
cross-section  and  of  two  compressive  cubes  whose  area  of  cross- 
section  was  7f  square  inches. 

TABLE   IV. 

Ultimate   Resistance  in  Lbs.  per  Square  Inch 


Neat 
Cement 

•a  *  '5 

l«5 

Mortars  Composed  of  1  Cement,  3  Fine  Gravel  by  Weight, 
Mixed  with  Trowel  to  Plastic  Consistency 

l|l 

s-a 

Mixed  With  and 

Mixed  With  and 

Mixed  With  and 

Mixed  With  Fresh 

Immersed  in 

Immersed  in 

Immersed  in 

Water  and  Kept 

Sea  Water 

SeaX 

7ater 

Fresh 

Water 

in 

Air 

Ace 

Ten- 

Ten- 

Ten- 

Com- 

Ten- 

Com- 

Ten- 

Com- 

sion 

sion 

sion 

pression 

sion 

pression 

sion 

pression 

4  Weeks... 

422 

149 

95 

T  T  C 

327 

71 

QQ 

469 

70 
77 

426 

I  Year  

736 

275 

1  \") 

179 

540 

146 

731 

173 

838 

It  will  be  seen  that  the  tension  and  compression  tests  do  not 
furnish  uniform  results;  the  tension  specimens  hardening  in  sea 
water  are  stronger  than  those  hardening  in  fresh  water.  This  is 
not  true  of  the  compressive  specimens,  whose  crushing  resist- 
ance, moreover,  is  exceptionally  low.  The  cement  used  in  these 


50 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


tests  had  the  following  fineness :  50  per  cent,  passed  a  sieve  hav- 
ing 32,300  meshes  per  square  inch;  31  per  cent,  passed  a  sieve  of 
5,800  meshes  per  square  inch,  but  was  retained  by  previous 
sieves,  and  the  remaining  cement  was  retained  on  the  5,800  mesh 
screen. 

It  may  then  be  concluded  that,  unless  mixtures  fail  by  disin- 
tegration, their  strength  under  sea  water  approximates  that  at- 
tained under  normal  conditions,  but  is  never  greater.  And, 
finally,  disintegration  may  be  avoided,  either  by  making  the 
mixture  impermeable  or  by  adding  some  substance  such  as  poz-- 
zalana. 

Gauging  with  Salt  Water — The  action  of  ordinary  salt  solu- 
tions on  the  strength  of  cement  mixtures  still  remains  to  be  con- 
sidered. 

Figure  i  is  taken  from  tests  reported  by  A.  Noble  in  Vol. 
XVL,  1887,  of  the  Transactions  of  the  American  Society  of 
Civil  Engineers.  The  figure  shows  the  effect  on  the  tensile 
strength  of  one  cement  to  one  sand  mortar  briquettes  when 
mixed  with  water  containing  various  percentages  of  salt,  it 
will  be  seen  that  there  is  but  very  little  loss  in  strength  when  the 

water  contains  small  per- 
centages of  salt,  and  not 
much  more  loss  even 
when  the  percentages  rise 
to  1 6. 

E.  C.  Clarke  records 
very  similar  experiments 
in  Vol.  XIV.  of  the  same 
Transactions;  in  this  case 
briquettes  were  gauged 
with  fresh  water  and  with 
salt  water,  and  were  also 
immersed  in  both  fresh  and  salt  water;  the  results  show  no  great 
variations  in  strength.  Clarke  states  that  the  time  of  setting  is 
somewhat  retarded;  in  this  he  is  corroborated  by  Heath,  page  83, 
of  his  Manual  of  Limes,  Cements  and  Mortars. 
C.  S.  Gowen  records  in  a  paper  read  before  the  American  So- 


18 
Months     Months 

Age  of  Specimens, 
FIG.  1.— NOBLE'S  TESTS. 


Zi 
Months 


Art  I5-] 


POROSITY  AND  PERMEABILITY. 


ciety  of  Testing  Materials,  July  3,  1903,  results  of  tensile  tests 
made  on  the  usual  standard  briquettes  as  to  the  effect  of  salt 
water  in  gauging  mortar  under  normal  laboratory  temperature 
conditions;  the  briquettes  were  composed  of  one  part  of  cement 
and  two  and  three  parts  of  quartz  sand.  It  will  be  seen  (Table 
V.)  that  at  the  end  of  a  year  there  is  no  appreciable  difference  in 
strength  between  the  specimens  which  were  gauged  with  fresh 
water  or  salt  water. 

The  salt  water  was  about  a  10  per  cent,  solution;  each  result 
shown  is  an  average  of  ten  breakings.  It  may  therefore  be  defi- 
nitely stated  that  gauging  cement  mixtures  with  salt  water  does 
not  affect  the  ultimate  strength  injuriously. 

TABLE  V. 


Age 

1:2  Briquettes                                       1:3  Briquettes 

Tensile  Strength  in  Lbs.  per  Square  Inch,  Gauged  with 

Fresh  Water 

Salt  Water 

Fresh  Water 

Salt  Water 

7  Davs 

236 
289 
414 
549 
554 
572 

126 
231 
294 
424 
452 
576 

112 
183 
268 
335 
351 
458 

68 
131 
215 
266 
301 
413 

I  Month  

3  Months 

9  Months 

12  Months  

Art.  15. — Porosity  and  Permeability. 

Porosity  and  permeability  are  terms  often  confused  in  meaning 
when  applied  to  cement  mixtures;  but  they  apply  to  entirely  dif- 
ferent properties.  Porosity  is  a  measure  of  the  voids  and  gives 
no  indication  .of  the  connection  of  these  voids  with  one  another. 
Permeability,  on  the  other  hand,  implies  paths  from  one  void  to 
another.  The  question  of  porosity  is  not  of  the  greatest  impor- 
tance, except  as  giving  indication  of  the  denseness  of  a  mixture 
and  perhaps,  indirectly,  an  indication  of  its  ultimate  strength. 

Due  to  the  fineness  of  grinding  and  to  the  uniformity  of  grain, 
it  is  to  be  expected  that  neat  cements  should  be  more  porous 
than  mixtures  of  sand  and  cement.  This  is  perhaps  the  more 
evident  when  neat  cement  is  compared  to  concrete,  since  in 
the  latter  possibly  50  per  cent,  of  the  mass  consists  of  large 
pieces  of  dense  stone.  However,  in  the  case  of  concrete,  it  is 
clear  that  paths  between  the  voids  are  more  likely  to  exist  than 


52  GENERAL  PHYSICAL  PROPERTIES.  [Ch.  III. 

in  the  case  of  neat  cement,  and  that,  therefore,  the  concrete  may 
be  the  more  permeable. 

R.  Feret,  in  a  very  valuable  paper*  published  in  Vol.  IV.,  1892, 
of  the  "Annales  des  Fonts  et  Chaussees,"  discusses  fully  the  po- 
rosity and  permeability  of  various  kinds  of  cement  mortars,  and 
shows  that  the  actual  solid  contents  of  a  mixture  are  clearly  indi- 
cated by  the  amount  of  water  absorbed.  He  states  that  a  mix- 
ture in  which  the  fine  sands  predominate  is  always  the  more 
porous;  the  permeability,  however,  varies  inversely  to  the  po- 
rosity. 

Feret's  experiments  were  carried  on  with  three  sizes  of  sand 
grains;  a  coarse  sand,  which  would  correspond  to  a  sand  passed 
by  a  No.  5  sieve  and  retained  on  a  No.  12  sieve;  a  medium  sand, 
which  would  correspond  to  a  sand  retained  between  a  No.  12  and 
a  No.  50  sieve,  and  a  fine  sand,  all  of  which  would  pass  a  No.  50 
sieve. 

Feret's  Conclusions — It  is  perhaps  best  to  quote  Feret's  con- 
clusions directly  :f 

(a)  The  permeability  of  a  mortar  depends  less  on  the  total  vol- 
ume of  the  voids  than  on  their  individual  dimensions. 

(b)  The  continuous  passage  of  water  through  mortars  dimin- 
ishes the  permeability  very  rapidly. 

(c)  The  filtration  of  sea  water  through  mortars  often  results  in 
their  more  or  less  rapid  disintegration. 

(d)  All  other  things  being  equal  at  the  beginning  of  filtration, 
plastic  mixtures  are  less  permeable  than  dry;  after  some  time 
this  difference  disappears,  and  it  appears  that,  in  the  case  of  sea 
water,  disintegration  is  not  more  rapid  for  one  than  for  the  other. 

(e)  In  general  mortars  made  with  the  same  sand  are  the  less 
permeable,  as  they  contain  the  more  cement. 

(f)  Mortars  of  the  same  richness,  but  of  different  granulometric 
sand  composition,  are  disintegrated  by  the  passage  of  sea  water 
as  rapidly  as  in  proportion  to  the  fine  grains  in  the  sand.     The  ef- 


*Sur  la  Compacite  des  Mortiers  Hydr antiques. 
}Page  143  of  Feret's  paper. 


Art.  I5-] 


POROSITY  AND  PERMEABILITY. 


fects  may  not  be  the  same  for  mortars  which  are  simply  placed  in 
water. 

A  very  full  discussion  on  impervious  concrete  is  also  recorded 
in  the  Transactions  of  the  American  Society  of  Civil  Engineers, 
December,  1903,  and  the  work  of 
various  experimenters  is  cited. 
The  general  conclusion,  there 
summarized  by  R.  W.  Lesley,  is 
as  follows:  That  neat  cement 
mortars  show  the  least  permea- 
bility; that  mortars  with  fine 
sand  are  less  permeable  than 
those  mortars  with  coarse  sand, 
and  that  the  lessening  of  the  per- 
meability is  due  to  the  closing  of 
the  pores  by  lime,  which  is  car- 
ried in  suspension,  in  the  process 
of  filtration,  through  the  mass, 
and  which  ultimately  forms  a 
coating  on  the  surface  of  the  ma- 
sonry. 

In  almost  all  cement  mixtures, 
even  if  permeability  does  exist  in 
the  beginning,  it  decreases  very 
fast  as  the  mixture  ages,  provided  disintegration  does  not  take 
place.  This  is  very  clearly  shown  by  experiments  reported  in 
Vol.  CVIL,  page  95,  of  the  Proceedings  of  the  Institution  of 
Civil  Engineers.  Figure  i  is  taken  from  that  report  and  shows 
the  filtration  of  sea  water  under  a  head  of  twenty-four  feet, 
through  one  cubic  foot  of  Portland  cement  concrete  of  the  pro- 
portions indicated,  three  months  old.  It  is  seen  how  rapidly  the 
amount  of  water  which  passes  through  the  mass  decreases  with 
the  time,  even  for  widely  varying  proportioned  mixtures. 

Figures  2  and  3  are  taken  from  Feret's  paper,  already  noted. 
Figure  2  shows  the  initial  permeability  of  two  series  of  mortars, 
mixed  with  different  proportions  of  sand  and  gauged  with  dif- 
ferent percentages  of  water.  The  size  of  the  specimens  and  the 


10  15 

Age  in  Days 

FIG.  1. 


54 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


surface  through  which  the  water  passed  are  not  given ;  the  speci- 
mens set  in  air  two  weeks  before  being  tested.  The  small  initial 
permeability  of  the  richer  mixtures  is  immediately  noted. 


7060 


3530 


Initial  Permeability 

of  2  Series  of  Mortars 

of  different  Consistencies 


\  7.3  Sand  4.9  Sand  3.6  Sand 

\    1  Cement  1  Cement    _       1  Cement 

Parts  of  Sand  to  Cement 

FIG.  2.-FERET'S  TESTS. 


Figure  3  shows  the  variation  in  the  permeability  of  three  mor- 
tars during  the  two  first  days  of  filtration;  the  experiments  were 
continued  for  one  year,  and  at  the  end  of  that  time  it  was  found 
that  the  percolation  through  the  lean  mixture  had  ceased,  but 


81180 


Variation  of  Permeability 
Of  3  Mortars  during  the 
first  days  of  flltratioa 


0        6      12  84  3&  4&    Bonra 

Time  Elapsed  from  Beginning  of  Filtration. 
FIG.  3.—  FERET'S  TESTS. 


that  the  other  richer  mixtures  had  been  slightly  attacked  by  sea 
water  and  were  passing  very  small  quantities  of  water. 

Feret  notes  that  tEe  permeability  decreases  the  more  rapidly  as 
the  first  filtration  is  the  more  abundant,  and  that  the  amount 


Art.  16.]       EFFECT  OF  FREEZING  ON  CEMENT  MIXTURES.  55 

passed  is  independent  of  the  nature  of  the  liquid  (fresh  or  sea 
water). 

In  conclusion,  inspection  of  existing  concrete  work  is  sufficient 
to  show  that  almost  any  well  balanced  mixture  can  be  made  im- 
pervious to  the  passage  of  liquids;  the  greatest  care  in  mixing, 
due  to  the  non-homogeneity  of  the  ingredients,  must  be  observed. 
Where  concrete  masses  do  pass  water,  the  permeability  will  in 
general  be  found  to  be  due,  not  to  some  defect  in  the  concrete 
itself,  but  to  open  cracks  which  may  have  been  caused  from  one 
of  various  reasons,  such  as  improper  joining  of  work  laid  at  dif- 
ferent times,  settlement  of  foundations  or  temperature  changes. 

The  addition  of  salts  or  soaps  to  cement  mixtures  to  cause  im- 
permeability has  not  been  considered  by  the  author;  although 
many  experiments  have  been  made  along  such  lines,  the  results 
are  not  in  such  form  as  to  warrant  the  drawing  of  definite  con- 
clusions, the  more  so  when  it  seems  possible  to  make  cement 
mixtures  impervious  without  such  aid. 

Art.  1 6. —The  Effect  of  Freezing  on  Cement  Mixtures. 

The  effect  of  cold  temperatures  on  the  setting  and  hardening 
of  cements  has  been  much  discussed,  but  appears  at  present  to  be 
very  simple.  It  is  now  the  opinion  that  the  hardening  properties 
of  frozen  cement  are  not  impaired,  if  the  freezing  has  taken  place 
before  the  initial  setting  of  the  cement  has  begun.  Under  those 
conditions  the  physical  action  of  the  changing  of  the  water  into 
globules  of  ice  has  prevented  the  chemical  action  of  the  crystalliz- 
ing of  the  cement  particles ;  crystallization  cannot  take  place  until 
the  ice  globules  return  to  the  liquid  form.  No  damage  will  then 
have  been  done,  if  freezing  does  not  again  take  place  before  the 
cement  has  set;  but  if  continued  thawing  and  freezing  take  place, 
allowing  an  intermittent  action  of  setting,  it  is  very  likely,  under 
those  conditions,  that  the  cement  will  be  injured.  Many  large 
pieces  of  concrete  work  have  been  built  in  freezing  weather  and 
have  remained  for  long  periods  of  time  in  a  frozen  condition,  but, 
after  thawing,  have  shown  no  evil  effects.  It  is  only  necessary  to 
bear  in  mind  that  the  physical  action  of  freezing  must  so  far  pre- 
cede the  beginning  of  the  chemical  action  as  to  preclude  the  lat- 


56  GENERAL  PHYSICAL  PROPERTIES.  [Ch.  III. 

ter's  taking  place.  The  use  of  salt,  glycerine  or  other  substances 
in  the  water  used  for  laying  cements  at  cold  temperatures  seems, 
therefore,  unnecessary,  more  particularly  as  there  is  always  the 
possibility  that  these  admixtures  may  prove  injurious. 

The  percentage  of  injury  done  by  the  addition  of  salt  sub- 
stances may  not  be  very  great,  and  may  often  be  nil,  but  it  is 
probable  that  the  use  of  these  adulterants  will  cease. 

Laboratory  experiments  made  to  determine  the  change  in 
strength  of  mixtures  gauged  with  salt  water  must  be  treated  with 
some  caution,  since  in  the  laboratory  the  experiments  are  made 
under  normal  temperature  conditions,  whereas  in  practice  salt  is 
added  to  cement  mixtures  only  during  freezing  weather;  the 
hardening  of  a  cement  under  the  latter  condition  may  be  very 
different. 

It  has  already  been  shown  in  a  preceding  article  that,  in  the 
case  of  laboratory  experiments,  there  is  but  little,  if  any,  decrease 
in  the  strength  of  the  mixture,  even  when  a  16  per  cent,  salt  solu- 
tion is  used.  Experiments  made  with  salt  mixtures  during  freez- 
ing weather  have  shown  very  similar  results;  but  it  seems  un- 
necessary at  the  present  time  to  record  such  experiments  in  any 
detail,  since,  as  has  already  been  stated,  concrete  mixed  with 
fresh  water  is  now  laid  at  almost  any  temperature,  and  is  found 
to  suffer  no  ill  effects,  if  alternate  freezing  and  thawing  do  not 
take  place.  For  such  experiments  with  salt  mixtures  the  reader 
is  referred  to  tests  made  by  E.  S.  Wheeler  and  recorded  by  him 
in  the  Report  of  the  Chief  of  Engineers,  U.  S.  Army,  for  1895, 
page  2968  and  following. 

The  following  experiments,  made  at  the  Watertown,  Mass., 
Arsenal  on  frozen  cement  mixtures,  gauged  with  fresh  water, 
are  of  exceeding  value. 

Table  I.  is  taken  from  the  Watertown  Arsenal  Report  for  1901, 
and  shows  the  crushing  strength  of  two-inch  cubes  which  were 
left  for  various  intervals  of  time  in  a  temperature  of  o  degrees 
and  were  then  exposed  to  a  temperature  of  70  degrees  Fahr. 
It  will  be  seen  that  the  compressive  strength  did  not  vary  to  any 
considerable  degree,  no  matter  how  long  the  specimen  had  been 
exposed  to  the  freezing  temperature,  if  it  had  been  exposed 


Art.  16.]      EFFECT  OF  FREEZING  ON  CEMENT  MIXTURES. 


57 


the  same  number  of  days  at  the  70  degree  temperature.  It  is 
clear  that  no  setting  action  takes  place  when  the  water  in  the 
mixture  is  frozen. 

The  results  of  tests  on  three  brands  of  cements  only  is  ab- 
stracted, since  these  are  characteristic  examples. 

Tables  II.  and  III.  show  the  ultimate  compressive  resistance 
of  two-inch  cubes  composed  of  neat  Portland  and  natural  ce- 
ments and  of  1:1  mortars  subjected  to  low  temperatures  at  the 
times  of  making.  These  experiments  are  also  recorded  in  the 
Report  of  the  Watertown  Arsenal  for  1901. 

TABLE  I. 


Brand 

Length  of  Time  at 
0°  F. 

Subsequent  Length 
of  Time  at  70°  F. 

Compressjve 
Strength    in 
Lbs.  per  Sq.  In. 

Months 

Days 

Days 



*) 

7 

846 



14 

7 

1000 

Star  I  :  I  Mortar  - 
Portland  Cement 

2 

21 
31 

7 
7 
7 

1010 
981 
981 

3 



7 

1010 



7 

7 

1470 



14 

7 

1230 

Josson  1:1  Mortar...' 



21 

7 

1240 

Portland  Cement 



29 

7 

1430 

3 



7 

1520 

{ 



6 

14 

540 



15 

14 

527 

Hoffman  1:1  Mortar.  < 



20 

14 

624 

Natural  Cement 



28 

14 

561 

1 

3 



14 

579 

In  Table  II.  there  were  three  general  groups  of  specimens; 
one  was  allowed  to  set  in  the  open  air  of  the  testing  laboratory 
at  the  ordinary  atmospheric  temperature,  given  in  the  report  as 
70  degrees  Fahr.  The  specimens  belonging  to  the  other  two 
groups  were  placed  in  a  cold  storage  warehouse,  where  they  re- 
mained different  intervals  of  time.  One  group  was  placed  in  a 
room  whose  temperature  was  maintained  at  about  39  degrees, 
and  the  other  group  in  a  room  whose  temperature  was  in  the 
vicinity  of  o  degrees.  Specimens  intended  for  this  last  room 
were  mixed  on  cold  days,  with  the  thermometer  in  the  neighbor- 
hood of  15  to  20  degrees  Fahr.,  and  it  was  intended  to  freeze  the 


58 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  -III. 


material  as  soon  as  practicable  after  mixing  and  use  mixtures  as 
wet  as  ordinarily  employed  in  construction.  The  table  shows 
clearly  the  lengths  of  time  the  various  specimens  were  left  under 
these  varying  temperature  conditions  and  the  length  of  time  at 
which  the  frozen  specimens  were  allowed  to  thaw  under  normal 
conditions.  Careful  examination  will  show  that  the  frozen  speci- 

TABLE  II. 


Compressive 

Strength  in  Lbs.  per 

Square  Inch 

Brand 

Specimens  Set  in  Air 
at  0°  F.,  and  Then 
Placed  in  Air 
at  70°  F. 

Specimens  Only  in 
Air  at  70°  F. 

Specimens  in  Air  at 
39°  F.,  and  Then 
Placed  in  Air 
at  70°  F. 

Star  Portland 

3  Mos.  and  30  Days 

362ft 

30  Days 
4^70 

Alsen  Portland  

2520 

3900 

Star  Portland 

1  Mo.  and  30  Days 
346ft 

30  Days 
4^70 

Star  I  *  I  Mortar 

1400 

I960 

Storm  KinjJ  Portland 

1680 

2520 

3  Mos.  and  14  Days 

TO  rr\ 

14  Days 
IQ7ft 

Alsen  Portland 

04^0 

3780 

64ft 

1  1  60 

1020 

800 

•S7Q 

808 

A39 

744 

Star 

3  Mos.  and  14  Days 
4410 

3  Mos.  and  14  Days 
42ftft 

Storm  Kinj(   •  •    •  • 

4  Months 
2380 

3  Mos.  and  1  Month 
2700 

•jc;i(-) 

64ftft 

3  Months 
31  10 

3  Mos.  and  8  Days 
4970 

3  Mos.  and  15  Days 
580 

3  Mos.  and  15  Days 
I4ftft 

3  Months 
1720 

3  Mos.  and  13  Days 
906ft 

Norton 

4  Months 

Qtf) 

3  Mos.  and  14  Days 

mens  exhibited  practically  no  deterioration  in  strength,  if  the 
time  allowed  them  under  normal  temperature  conditions  was 
equal  to  that  of  the  specimens  of  the  same  mixture  to  which 
they  could  be  compared. 

The  specimens  noted  in  Table  III.  were  treated  a  little  differ- 
ently;, the  frozen  specimens  were  kept  frozen  for  various  inter- 


Art.  16.]       EFFECT  OF  FREEZING  ON  CEMENT  MIXTURES. 


59 


vals  of  time  up  to  one  year  and  then  allowed  to  set  for  one  day 
only  under  normal  temperature  conditions.  It  will  be  seen  that 
the  strength  of  the  frozen  material  increased  to  some  extent, 
showing  some  faint  chemical  action;  but  in  no  case  did  a  frozen 
specimen  one  year  old  attain,  even  approximately,  the  strength 
of  a  normal  specimen  one  month  old. 

C.  S.  Gowen  presented  a  paper  before  the  American  Society 
of  Testing  Materials,  July  3,  1903,  in  which  are  also  recorded 
some  tests  on  Portland  cement  mortar  exposed  to  various  cold 
temperatures.  The  tests  were  made  on  the  standard  form  of 

TABLE  III. 


Brand 

Compressive  Strength  in  Lbs.  per  Square  Inch 

Specimens  Set  in  Air  at  Temperature 
0°  F.  (One  Day  in  Air  at  70°  F. 
Before  Testing) 

Specimens  Set  in  Air 
at  70°  F. 

1  Month 

3  Months 

1  Year 

1  Month 

3  Months 

Star  Portland              

1350 
383 
749 
986 
347 
238 
411 
206 
341 
225 

1720 
497 
703 
1210 
624 
241 
478 
276 
347 
274 

2724 
864 
1370 
1580 
802 
333 

428 
680 
358 

4350 

2520 
3900 
3970 
724 
1  140 
1  140 
1000 
1560 

4400 

2430 
4040 
3110 
661 
1720 
1070 
1090 
1240 

Star  I  *  I  Mortar          

Storm  King  Portland  

Obelisk  Natural       •  •    •  •  •  • 

534 

637 

1015 

2256 

2085 

tensile  briquettes,  composed  of  one  part  Giant  Portland  cement 
and  two  parts  of  crushed  quartz  sand.  Table  IV.  shows  the  re- 
sults obtained  under  normal  temperature  conditions;  Table  V., 
results  obtained  under  freezing  temperature.  In  the  latter  table 
each  figure  is  an  average  of  eight  tests.  It  should  be  noted  that 
the  results  recorded  for  the  six  months  freezing  temperature  are 
subject  to  an  error,  due  to  the  fact  that  the  briquettes  were  con- 
tinually in  air  up  to  that  time  and  were  probably  dried  out.  The 
briquettes  of  nine  and  twelve  months,  made  under  the  same  con- 
ditions, were  placed  in  water  at  the  end  of  six  months,  and 
showed  uniform  increase  in  strength  over  the  strength  of  one 
and  three  months. 


60 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


TABLE  IV. 


Tensile  Strength  of  1:2  Mortar  Briquettes 


Age 

Number  of  Specimens 
Broken 

Average  Tensile  Strength 
in  Lbs.  per  Sq.  In. 

28   Days 

690 

441 

3  Months 

215 

563 

185 

657 

9  Months 

I*)*) 

671 

12  Months         .            

165 

663 

TABLE  V. 


Tensile  Strength  of  1:2  Mortar  Briquettes 


Tensile  Strength  in  Lbs.  per  Square  Inch  at  Age  of 


oenes 

28  Days 

3  Months 

6  M  nths 

9  Months 

12  Months 

A  

370 

474 

366 

553 

553 

B  

458 

455 

347 

381 

586 

c  

371 

413 

314 

452 

510 

D 

272 

360 

287 

567 

602 

E  

255 

246 

300 

437 

512 

Series  A.  Placed  in  cold  air,  24-32  deg.  F.,  immediately  after 
mixing;  fresh  water  used. 

Series  B.  Placed  in  cold  air,  24-10  deg.  F.,  immediately  after 
mixing;  fresh  water  used. 

Series  C.  Placed  in  cold  air,  24-32  deg.  F.,  after  taking  heavy 
Gillmore  needle ;  fresh  water  used. 

Series  D.  Placed  in  cold  air,  20-10  deg.  F.,  immediately  after 
mixing;  brine*  used. 

Series  E.  Placed  in  cold  air,  20-10  deg.  F.,  immediately  after 
mixing;  fresh  water  used. 

J.  S.  Costigan  records  in  the  Transactions  of  the  Canadian 
Society  of  Civil  Engineers,  1903,  some  interesting  tests  on  the 
effects  of  freezing  neat  cements,  in  which  various  briquettes  were 
moulded  under  a  pressure  of  twenty  pounds  per  square  inch. 
When  these  briquettes  were  twenty-four  hours  old  they  were  all 
placed  in  water  and  allowed  to  remain  there  until  they  were 
seven  days  old,  with  the  exception  of  some  twenty-four  hours 
during  this  period,  when  they  were  exposed  to  the  action  of 


* About  10  %  by  weight,  solution. 


Art.  17.] 


ADHESION  OF  IRON  IN  CONCRETE. 


61 


frost  for  twenty-four  or  forty-eight  hours.  The  results  show  al- 
most a  uniform  ultimate  resistance,  no  matter  at  what  period 
after  making  the  specimens  they  were  subjected  to  the  freezing 
conditions. 

Reviewing  these  recorded  experiments,  it  may  be  seen  that  no 
fear  need  be  apprehended  if  specimens  are  frozen  once  only  and 
then  thawed  out.  The  ultimate  strength  attained  under  those 
conditions  is  not  appreciably  lower  than  that  attained  under  nor- 
mal conditions. 

Art.  17 — Adhesion  of  Iron  in  Concrete. 

Table  I.  shows  the  adhesion  of  iron  rods  in  concrete,  as  found 
by  E.  Morsch  and  reported  by  him  in  "Beton  und  Eisen,"  Part 
III.,  1903.  It  will  be  seen  that  the  adhesion  varies  not  only 
with  the  richness  of  the  cement  mixtures,  but  also  with  the  per- 
centage of  water  used  in  gauging. 

TABLE  I. 


Percentage  of  Water 

Adhesion  in  Lbs.  per  Square  Inch 

,                                Richness  of  Mixture 

1:1 

1:2 

1:3 

1:4 

1:5 

1:6 

1:7 

1:8 

10  Per  Cent  
15  Per  Cent  
20  Per  Cent  

213 
655 
398 
313 

270 
696 
398 
427 

270 
569 
356 
328 

370 
540 
356 
342 

427 
299 
171 
114 

384 
270 
171 
170 

237 
213 
156 
128 

171 
142 
100 
100 

25  Per  Cent  

The  table  exhibits  no  positive  fact,  although,  in  general,  the 
richer  mixture  furnishes  the  greater  adhesion.  Neither  too  little 
nor  too  much  water  is  to  be  used  in  the  mixing,  since  some  in- 
termediate percentage  furnishes  the  greatest  adhesion. 

Professor  Charles  Spofford  made  a  series  of  tests  upon  the  hold- 
ing power  of  different  types  of  rods,  which  are  reported  in  the 
same  number  of  the  publication.  The  concrete  used  was  a 
Portland  cement  concrete  of  1 13 :6,  the  stone  used  being  a  mix- 
ture of  two  parts  of  one-inch  trap  and  one  part  of  one-half-inch 
trap.  The  concrete  was  wet  sufficiently  so  that  when  tamped 
into  the  moulds  water  flushed  to  the  surface.  The  rods  were  all 
thoroughly  cleaned  by  a  sand  blast  before  the  concrete  speci- 
mens were  made.  Several  types  of  rods  were  used — the  Ran- 


62 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


some  rod,  which  is  a  square  rod,  but  twisted  through  an  angle  of 
20  degrees ;  the  Thacher  rod  and  the  Johnson  rod  (the  two  latter 


TABLE  II. 


Type  of  Rod 

Cross  Sec- 
tion of  Rod 
in  Inches 

Mean  Area  of 
Cross  Sec- 
tion of  Rodin 
Sq.  Inches 

Cross  Sec- 
tion of  Con- 
crete Block 
in  Inches 

Length 
of  Rod 
Imbedded 
in  Inches 

Greatest 
Adhesion 
in  Lbs. 
per 
Sq.  In. 

I 

Remarks 

Ransome  

1A    X    l/2 

0.25 

6x6 

12 

454 

> 

16 

228 

o 

t4 

44 

44 

44 

26 

291 

I 

44 

44 

44 

8x8 

12 

310 

I 

44 

44 

44 

16 

396 

8 

4          " 

44 

44 

" 

26 

260 

# 

,, 

%  x  # 

0.56 

44 

20 

388 

Cfl"-' 

.4 

44 

24 

399 

Iff 

4, 

44 

44 

44 

36 

305 

2£ 

44 

ilA  x  iyi 

1.27 

10     X     10 

27 

245 

Sg. 

44 

37 

HI 

w  8: 

—.3 

44 

44 

« 

44 

50 

138 

LoJ2: 

Thacher 

Yz  x  y> 

0.18 

6x6 

12 

222 

Sn 

16 

282 

1* 

,, 

44 

44 

44 

26 

223 

.  82 

4. 

V  x  % 

0.39 

8x8 

20 

402 

LftJ 

,4 

24 

290 

<  V 

44 

44 

44 

44 

36 

250 

&l 

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l*/8  X  ll/8 

1.03 

10  x  10 

27 

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£8. 

,, 

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304 

Is 

44 

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// 

50 

268 

«" 

Johnson.        . 

Yz  x  y* 

0.19 

6x6 

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508 

0  0. 

16 

410 

»5" 

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44 

44 

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26 

264 

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%  x  K 

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t, 

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Plain          ... 

3/  round 

0.44 

8x8 

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271 

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31 

255 

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%  x  # 

0.56 

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1,      C£ 

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145 

Art.  17.]  ADHESION  OF  IRON  IN  CONCRETE.  63 

being  well  known  forms  of  specially  rolled  rods),  and  also  plain 
round,  square  and  flat  rods.  All  tests  were  made  twenty-eight 
days  after  mixing  of  the  concrete. 

Table  II.  shows  the  value  of  the  adhesion  in  pounds  per 
square  inch  obtained  by  these  different  bars.  Of  the  various 
plain  forms,  it  will  be  seen  that  the  round  bars  show  the  greatest 
adhesion  and  the  flat  bars  the  least.  In  general  the  adhesion  de- 
creased as  the  depth  to  which  the  rods  were  imbedded  was  in- 
creased, but  no  conclusive  superiority  of  one  kind  of  bar  as  com- 
pared to  another  can  be  shown;  moreover,  in  many  cases  the 
rods  did  not  pull  out  at  failure,  but  the  blocks  were  split.  The 
true  adhesion  was  not  found  in  those  cases. 

Table  III.  shows  the  values  of  adhesion  of  round  iron  rods,  de- 
termined by  Professor  W.  K.  Hatt  and  reported  by  him  before 
the  American  Section,  International  Association  for  Testing  Ma- 
terials, at  its  annual  meeting  of  1902.  The  table  gives  averages 
of  three  tests  each,  the  concrete  being  a  mixture  of  1:2:4  and  its 
age  about  thirty-two  days. 

TABLE  III. 


Size  of  Rod 

Depth  of  Rod  in  Concrete 
in  Inches 

Ultimate  Adhesion  in  Lbs.  per 
Sq.  In.  of  Rod  Surface 

7-16  Inch  

6  0 

636 

5-8  Inch  

6.4 

7^6 

E.  S.  Wheeler  records,  on  page  2940  of  the  Report  of  the 
Chief  of  Engineers,  U.  S.  Army,  for  1895,  a  considerable  number 
of  tests  made  upon  the  adhesion  of  iron  bars  in  cement  mixtures. 
In  the  first  set  of  experiments,  shown  in  Table  IV.,  the  mixture 
was  composed  of  one  part,  by  weight,  of  Portland  cement  to  two 
parts  of  sand,  the  latter  being  limestone  screenings  passing  f-inch 
slits;  the  age  of  the  mortar  was  one  month.  The  bars  were  im- 
bedded to  depths  varying  from  8  to  10  inches;  they  were  in  the 
form  of  bolts,  being  cut  from  bar  iron,  and  were  without  fox 
wedges.  The  twisted  bolts  were  formed  by  twisting  a  piece  of 
one-inch  square  bar  iron,  the  length  of  the  twisted  portion  being 
8  inches.  The  periphery  of  a  twisted  bolt  was  taken  to  be  the 
circumference  of  a  circle  whose  diameter  was  the  distance  be- 


64 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


tween  opposite  corners  of  the  bolt  after  twisting;  a  core  of  mortar 
of  this  diameter  was  torn  from  the  bar  in  pulling.  It  is  seen  that 
the  increase  in  resistance  of  the  -twisted  to  the  plain  bar  is  not 
very  great. 

The  tests  shown  in  Table  V.  differ  only  in  that  ordinary  river 
sand  was  used,  the  mixtures  used  being  neat,  1 :2  and  1 14.  The 
bolts  were  imbedded  2  to  10  inches. 

TABLE   IV. 


Description  of  Bolt 

Mortar 

Number 
of  Bars 
Tested 

Average  Adhe- 
sion in  Lbs. 
per  Sq.  Inch 

Plain    Vz  In    Diameter,  Round  

I  Cei 

nent,  1  S 

and 

3 
3 
3 
3 
4 
3 
3 
3 
3 

447 

556 
524 
543 
562 
434 
608 
516 
561 

Plain,  1%  In.  Diameter,  Round  

Plain    I  In    Square  .                   ...... 

Plain    \%  In    Square   

I  In.  Sq.,  Twisted  I  Turn  in  8  Ins.. 
I  In.  Sq.,  Twisted  1  Turns  in  8  Ins. 
I  In.  Sq.,  Twisted  3  Turns  in  8  Ins. 

In  the  Watertown  Arsenal  Report  for  1901  are  reported  vari- 
ous tests  made  on  the  adhesive  resistance  of  JxJ  inch  steel  bars 
imbedded  in  Portland  cement  concrete  prisms  6x6x18  inches 
long.  The  age  of  the  prisms  was  about  thirty  days  and  their 
average  crushing  resistance  about  2,278  pounds  per  square  inch. 
It  was  found  that  the  adhesion  of  the  rods  per  square  inch  aver- 

TABLE  V. 


Mortar 

No.  of  Bars  Tested 

Average  Adhesion  in 
Lbs.  per  Sq.  In. 

5 

7T7 

11 

264 

10 

III 

All  bolts  were  plain,  1  inch  in  diameter,  and  round. 

aged  204  pounds  per  square  inch  of  surface,  with  a  maximum 
value  of  296  pounds  and  a  minimum  of  77  pounds  per  square 
inch.  Three  other  prisms,  whose  crushing  resistance  was  4,210 
pounds  per  square  inch,  gave  an  average  adhesion  of  297  pounds 
per  square  inch.  The  rods  were  imbedded  various  lengths  from 
2  to  12  inches. 


Art.  17.] 


ADHESION  OF  IRON  IN  CONCRETE. 


65 


Considere  has  made  some  experiments  upon  the  adhesion  of 
iron  rods  in  concrete  in  a  different  way  from  other  experiment- 
ers; and  since  his  values  are  calculated  upon  an  assumed  condi- 
tion of  internal  stress,  too  much  weight  should  not  be  placed  on 
these  results.  His  values  for  iron  wire  of  .17  inch  diameter, 
whose  surface  was  perfectly  clean,  shining,  and  possibly  some- 
what greasy,  were  found  to  vary  from  70  to  170  pounds  per 
square  inch  of  surface,  for  concrete  kept  in  the  air.  The  re- 
sistance to  sliding  increased  to  256  pounds  for  prisms  of  the 
same  concrete,  reinforced  by  larger  rolled  iron  rods  .24  inch  in 
diameter,  and  in  other  experiments,  in  which  the  surface  of  the 
.17  inch  diameter  iron  wires  was  slightly  rusted,  the  sliding  re- 
sistance varied  from  330  to  500  pounds  per  square  inch.  In 
these  last  tests  the  specimens  were  kept  under  water.  He  found 

TABLE   VI. 


Diameter  of  Wire 
in  Inches 

Condition  of  Wire  Surface 

Resistance  per  Sq.  In. 
of  Surface  at  Cessa- 
tion of  Adherence 
in  Lbs. 

Resistance  per  Sq.  In. 
of  Wire  Rod  at  Ces- 
sation of  Adher- 
ence in  Lbs. 

0.14 
0.12 
0.10 

41 

Smooth 
Barbed,  with  Split  Ends 
Smooth 
Barbed,  with  Split  Ends 
Smooth 
Barbed,  with  Split  Ends 

502 

493 
442 
423 
286 
356 

33500 
33100 
35200 
34000 
27400 
34100 

that  the  resistance  to  sliding  bore  some  relation  to  the  amount  of 
water  used;  for  instance,  in  three  prisms  made  alike  and  in 
which  the  first  had  an  excess  of  water,  the  second  was  normal 
concrete  and  the  third  was  too  dry,  the  resistances  were  respect- 
ively 155,  170  and  70  pounds  per  square  inch. 

De  Joly  records  in  Vol.  III.,  1898,  of  "Annales  des  Fonts  et 
Chaussees,"  some  very  interesting  experiments  which  he  made 
on  the  adhesion  of  anchor  rods  fastened  by  means  of  neat  Port- 
land cement  in  holes  drilled  in  granite  blocks.  Three  sizes  of 
round  iron  rods  were  used — .14,  .12  and  .10  inches  in  diameter. 
The  depth  of  the  holes  in  the  granite  blocks  was  23.6  inches. 
The  cement  was  allowed  to  harden  one  month  in  air.  De  Joly 
comes  to  this  very  interesting  conclusion :  That  the  ultimate  ad- 


66  GENERAL  PHYSICAL  PROPERTIES.  [Ch.  III. 

hesive  resistance  does  not  depend  on  the  surface  of  contact  be- 
tween the  two  materials,  but  on  the  elastic  limit  of  the  inserted 
iron  rod. 

Table  VI.,  which  is  characteristic  of  several  series  of  experi- 
ments, shows  how  the  adhesive  resistance  per  square  inch  of 
contact  surface  varies  at  the  cessation  of  adherence  between  the 
two  materials  from  286  to  502  pounds  per  square  inch ;  but  if  the 
adhesive  resistance  is  expressed  in  pounds  per  square  inch  of  the 
rod  cross-section  the  values  so  obtained  show  no  very  great 
variation  for  the  different  sizes  of  rods. 

Experiments  are  recorded  by  De  Joly  for  various  qualities  of 
iron  rods  and  show  very  uniform  results,  according  to  this 
method  of  reasoning,  which  is  correct,  when  the  length  of  bar 
imbedded  is  so  great  that  the  ultimate  resistance  developed  by 
the  adhesion  is  greater  than  the  resistance  of  the  imbedded  bar 
at  its  elastic  limit. 

In  conclusion,  it  seems  proper  to  take  the  ultimate  adhesive 
resistance  of  iron  rods  in  concrete  as  between  250  and  400 
pounds  per  square  inch  of  surface. 

Art.  1 8.— The  Fatigue  of  Cement  Mixtures. 

The  question  of  the  fatigue  of  cement  mixtures  has  lately  re- 
ceived some  discussion,  although  the  matter  is  probably  not  of 
the  very  greatest  importance.  Professor  J.  L.  Van  Ornum  has 
presented  in  the  Transactions  of  the  American  Society  of  Civil 
Engineers,  December,  1903,  a  paper  in  which  he  records  com- 
pressive  tests  made  upon  neat  Portland  cement  cubes  two  inches 
on  the  side,  which  were  crushed  when  four  weeks  old.  The  ulti- 
mate strength  was  determined  in  the  usual  way  with  one  con- 
tinuous application  of  the  load,  and,  in  addition,  similar  blocks 
were  subjected  to  repeated  loadings  of  certain  percentages  of  the 
ultimate  strength,  varying  from  95  to  55  per  cent,  of  the  same. 
In  the  latter  case  the  load  was  applied  and  removed  repeatedly 
until  failure  occurred.  Figure  I  shows  the  results  obtained  from 
ninety-two  tested  blocks. 

The  same  subject  has  also  been  considered  by  De  Joly,  who 
has  recorded  the  results  of  his  experiments  in  "Annales  des 


Art.  18.] 


THE  FATIGUE  OF  CEMENT  MIXTURES. 


67 


S  g  8  3  §  8 

<q.  **  >*.  **.  ^  'a^. 
ercentage  of  Load  applied 

\ 

X. 

=-— 

=; 

Fonts  et  Chaussees,"  Vol.  III.,  1898.     He  experimented  on  the 
usual  type  of  tensile  briquette,  whose  ultimate  tensile  resistance 

for  one  application  of  a  load 

was  first  found.  Similar 
specimens  of  the  same  age 
were  then  tested  under  re- 
peated applications  of  a 
stress  considerably  lower 
than  the  ultimate,  and  it 
was  found  that  the  speci- 
mens broke  under  a  vary- 
ing number  of  repetitions. 
This  number  of  repetitions  increased  rapidly  with  the  age  of  the 
specimens. 

In  Table  I.,  which  is  characteristic  of  a  series,  De  Joly  shows,  for 
instance,  that  a  specimen  which  broke  under  a  tensile  load  of  187 
pounds  at  the  end  of  two  days  could  naturally  not  sustain  a  load 
of  200  pounds  per  square  inch,  but  that  at  the  end  of  three  days, 
when  one  application  of  276  pounds  caused  failure,  it  required 

TABLE  I. 


3000 
Number  of  Repetitions  producing  failure 

FIG.  1. 


Brand  of  Cement 

Age  of 
Specimen 
in  Days 

Average  Ultimate  Tensile 
Resist,  in  Lbs.  per  Sq.  In. 
One  Application  of  Load 

No.  of  Application  of  Ten- 
sile Stress  of  200  Lbs.  per 
Sq.  In.  Before  Rupture 

Candlot    

2 

187 

o 

3 

276 

18 

4 

390 

346 

tj 

405 

2815 

6 

505 

^>2I720 

Demarle 

17 
3 

665 
212 

105600 

5 

347 

97 

7 

420 

^5000 

eighteen  applications  of  200  pounds  per  square  inch  to  cause 
rupture.  The  table  is  otherwise  self-explanatory.  De  Joly's  ex- 
periments were  performed  so  that  the  time  of  application  of  each 
load  was  almost  instantaneous,  being  approximately  i-io  of  a 
second. 

In  order  to  determine  the  effect  of  a  slower  application  of  a 
load,  De  Joly  made  a  series  of  experiments,  the  results  of  which 


68 


GENERAL  PHYSICAL  PROPERTIES. 


[Ch.  III. 


are  shown  in  Table  II.     In  this  case  the  rapidity  of  the  applica- 
tions varied  from  92  to  26  per  minute,  and  it  will  be  seen  how 

TABLE  II. 


Age  of 
Specimens 
in  Days 

Ultimate  Tensile 
Resistance  in  Lbs. 
S;r  Sq.  In.,  with 
ne  Application 
of  Load 

Number  of  Applications  of  a  Load,  Intensity  of  200  Lbs. 
per  Square  Inch  Before  Rupture 

Rate  of  Application 

92  per  Minute 

52  per  Minute 

26  per  Minute 

4 
5 

6 
7 

271 
328 

361 
364 

0 
7 

36 

16 

2 
34 

174 
173 

75 
398 
More  than 
2300 
None  less  than 
3000 

very  rapidly  the  number  of  applications  increased  as  the  time  be- 
tween applications  increased.  Table  I.  seems  to  indicate  that 
there  might  be  a  limit  of  fatigue  to  a  material,  so  that  a  load,  if 

TABLE  III. 


Brand  of 
Cement 

Age  of 

Briquette 

Number  of 
Applications 
pf  Tensile 
Load  of  200 
Lbs.  per 
Sq.  In. 

Ult.  Resistance  in  Lbs.  per  Sq.  In. 

Remarks 

After  One  Appli- 
cation of  Load 

After  Treatment 
as  in  Column  3 

Ten- 
sion 

Com- 
pression 

Ten- 
sion 

Com- 
pression 

Demarle  . 

12  days 

5000 

558 

4800 

507 

4900 

(No  rest  after 
\  repeated  load- 

(ing. 

Demarle  . 

14     " 

" 

525 

5380 

521 

5070 

(Tested  24  hrs 
{  after  repeated 

(loading. 

Demarle  . 

7     " 

6500 

421 

3600 

400 

3620 

UK   hrs'  rest 
<  after  repeated 

(loading. 

Demarle  . 

15     " 

20000 

560 

6400 

545 

6170 

!No  rest  after 
repeated  load- 

Demarle . 

20     " 

*« 

573 

6900 

523 

6950 

ing. 
(48    hrs'    rest 
\  after  repeated 

(loading. 

Demarle  . 

\Yz  years 

« 

857 

14800 

834 

13450 

(48    hrs'    rest 
<  after  repeated 

(loading. 

Candlot.  . 

7  days 

40000 

552 

5350 

490 

5420 

(  No  rest  after 
j  repeated  load- 

Candlot.  . 

II     " 

,, 

576 

7300 

545 

7100 

(  Av'ge  12  hrs' 
jrest  after  re- 

(  peated  load'g 

Sollier.  .  . 

4X  nionths 

" 

681 

9470 

618 

9860 

(No  rest  after 
]  repeated  load- 

(ing. 

Sollier.  .  . 

5 

" 

708 

10200 

666 

10300 

(48    hrs'  rest 
j  after  repeated 

(loading 

Demarle  . 

1^  years 

" 

848 

14400 

826 

I4IOO 

(48    hrs'    rest 
\  after  repeated 

(loading. 

Art.  18.]  THE  FATIGUE  OF  CEMENT  MIXTURES.  69 

applied  sufficiently,  although  below  the  rupture  point,  might 
finally  cause  failure.  Table  II.  shows,  however,  that,  given  suffi- 
cient time  between  applications,  the  material  may  not  sustain 
any  injury. 

Table  III.  is  also  abstracted  from  De  Joly's  paper;  it  shows 
the  ultimate  tensile  and  crushing  resistance  of  a  cement  of  vari- 
ous ages,  first,  when  subjected  to  only  one  application  of  the 
final  load,  and  also,  of  similar  specimens,  after  the  elapse  of 
various  periods  of  time  after  having  been  subjected  to  repeated 
applications  of  a  tensile  stress  of  200  pounds  per  square  inch. 
Each  result  shown  is  an  average  of  three  tests,  the  specimens 
used  being  the  French  type  of  tensile  briquette. 

It  will  be  seen  in  this  case  that,  although  the  final  tensile  re- 
sistance is  slightly  lowered,  no  appreciable  change  occurs  in  the 
compression  pieces. 

It  will  require  many  experiments  of  a  character  similar  to 
these  quoted  to  determine  definitely  whether  there  is  in  concrete, 
as  there  is  in  steel,  a  critical  point  above  which  the  material 
should  never  be  stressed  if  it  is  never  to  fail  at  loads  below  the 
usual  ultimate  resistance. 


CHAPTER  IV. 
ELASTIC  PROPERTIES  IN  GENERAL. 

Art.  19.  —  Treatment  of  Stress-Strain  Curve. 

The  deformation  that  appears  in  a  material  which  is  subjected 
to  any  form  of  stress  determines,  in  connection  with  the  stress, 
its  elastic  properties.  A  diagram  which  shows  the  stress-strain 
relations  throughout  the  entire  range  of  stress  is,  therefore,  of 
great  assistance  in  showing  clearly  the  elastic  properties  of  any 
material. 

In  direct  tension  and  compression  tests  this  diagram  consists 
of  a  curve  which  shows  the  relative  elongation  or  shortening  of 
the  specimen  for  each  intensity  of  stress;  in  flexure  tests  the 
curve  illustrates  the  ratio  between  deflections  and  the  loads  ap- 
plied, and  in  torsion  tests  the  ratio  between  the  twist  and  the  ap- 
plied moment.  In  this  treatise,  however,  torsion  stresses  will  not 
be  considered. 

The  stress-strain  curve  for  tension  and  compression  speci- 
mens needs  no  explanation,  but  it  will  be  well  to  consider  its 
algebraic  equivalent.  The  general  designation  of  this  relation  is 
the  coefficient  or  modulus  of  elasticity.  It  is  usually  denoted  by 
E  and  expresses  the  ratio  for  any  stress  between  the  unit  stress  / 
and  the  unit  strain  /;  that  is, 


This  ratio  E  does  not  possess  a  constant  value  for  any  ma- 
terial between  a  point  of  no  stress  and  the  ultimate;  that  is,  the 
ratio  is  never  represented  by  a  straight  line  between  the  origin  of 
co-ordinates  and  the  point  representing  the  breaking  load.  The 
curve  is,  indeed,  very  complex  for  the  majority  of  materials  used 
in  construction;  but  it  is  a  straight  line  from  the  zero  stress  to  a 


Art.  19.] 


TREATMENT  OF  STRESS-STRAIN  CURVE. 


71 


point  called  the  elastic  limit,  the  latter  point  being,  in  fact,  that 
point  where  E  changes  in  value. 

In  the  case  of  some  materials  it  has  been  found  that  every 
stress,  however  small,  causes  a  permanent  strain  or  set  to  remain 
in  the  specimen  after  the  removal  of  the  stress.  This  involves 
slightly  the  proper  method  of  calculating  E.  It  may  be  deter- 
mined by  dividing  the  unit  stress  either  by  the  total  unit  strain 
in  the  specimen  or  by  the  elastic  unit  strain,  which,  is  the  total 
unit  strain  less  the  unit  set.  In  the  opinion  of  the  author,  the 
proper  method  to  employ  is  the  second,  which  determines  what 
will  be  called  hereafter  the  ''elastic"  coefficient  of  elasticity. 


2000 
1900 
1300 
1700 
1600 
£1500 
SfliOO 
Il300 

31200 

B  1100 

fUN 

•3  900  . 

xx 

1 

/ 

/ 

/ 

// 

/ 

x 

X 

// 

1-5 

J 

y 

v  •£> 

//: 

Q 

2 

4& 

,*?*? 

P 

r 

Z3 

^r 

Cylindrical  Specimen 
of  Neat  Cement 
Height    39.4  Inches  1 
Diameter    9t8  Inches  ) 
89  Days  Old 
Reported  by  Bach. 
Zeitsch.  Ver.Deutsh.Iiig. 
Nov.  28,  1896 

r% 

I2g^ 

£  800 

|TOO 
I600 

0  500 
100 
300. 
200 

100; 

5 

gin 

B 

^ 

r 

/? 

i 

<? 

r 

&* 

i 

/y 

j\ 

,  / 

/ 

156789 
Decrease  in  Length  per  Inch  of  Specimen.in..0001  Ins. 

FIG.  1. 

This  method  is  illustrated  by  Figure  i,  which  is  taken  from  a 
test  on  a  round  cylindrical  specimen  of  neat  cement  39.4  inches 
high,  9.8  inches  in  diameter  and  89  days  old,  reported  by  Pro- 
fessor C.  Bach  in  the  "Zeitschrift  des  Vereines  Deutscher  In- 
genieure,"  February  28,  1896.  Three  curves  are  shown,  the 
curve  marked  elastic  strain  being  obtained  by  subtracting  from 
the  curve  of  total  strain  the  curve  of  sets.  The  curve  of  sets  it 


72  ELASTIC  PROPERTIES  IN  GENERAL.  [Ch.  IV. 

should  be  noted,  is  obtained  by  determining  for  the  load  indi- 
cated in  the  figure,  the  strain  remaining  in  the  material  after  the 
load  is  entirely  removed.  This  curve  of  elastic  strain  may  be  ex- 
pressed by  an  algebraic  e'quation,  which  Professor  Bach  thinks 
may  take  the  following  form  : 

*=  ........       (2) 


in  which  E  represents  the  coefficient  of  elasticity;  p,  the  unit 
stress  applied  to  the  specimen;  /,  the  corresponding  elastic 
strain,  and  n,  a  numerical  exponent.  As  already  explained,  In 
the  case  of  a  majority  of  materials  used  in  engineering  work, 
this  curve  of  elastic  strain  is  a  straight  line  up  to  the  elastic  limit. 
For  that  portion  of  the  curve  the  coefficient  n  becomes  equal  to 
i  and  the  coefficient  of  elasticity  is  a  constant  quantity. 

dp 
To  find  the  tangent  of  the  inclination   —    of  this  stress-strain 

curve  at  any  point,  it  is  only  necessary  to  differentiate  the  equa- 

pn 

tion  E= — .     There  will  then  be  obtained 


dl 

When  /  equals  o,  and  when  n  is  greater  than   I,  Eq.  3  shows 

that  —  =OC,  and  the  tangent  becomes  vertical  at  the  origin  of  co- 
dl 

dp 
ordinates.     If  n  is  less  than  i,  and  for/=o,  —=ot  and  the  tan- 

dp 

gent  is  horizontal  at  the  same  point.     If  n  equals  i,  then  —  =£ 

dl 

and  the  coefficient  is  a  constant  quantity. 

Another  method  of  calculating  E  determines  what  might  be 
called  the  instantaneous  value  of  the  coefficient  of  elasticity,  and 
is  obtained  by  finding  the  elastic  strain  occurring  between  any 
two  applied  loads  and  assuming  that  the  curve  is  a  straight  line 
between  two  such  points.  This  involves  no  particular  error  if 
the  points  chosen  are  sufficiently  near  together. 

Again,  the  value  of  the  coefficient  of  elasticity  has  been  de- 


Art.  19.1  TREATMENT  OF  STRESS-STRAIN  CURVE.  73 

termined  by  finding  the  elastic  strain  between  the  initial  load  and 
any  other  load,  assuming  a  straight  line  between  two  such  points. 
If  the  curve  is  very  flat,  this  also  involves  but  very  little  error. 

Many  experimenters  ignore  entirely  the  curve  of  sets  and  cal- 
culate the  coefficient  of  elasticity  wholly  from  the  curve  of  total 
strain.  This  does  not  determine  the  proper  quantity,  although 
it  is  the  quantity  which  many  investigators  derive. 

The  method  of  determining  the  instantaneous  coefficient  of 
elasticity  is  really  equivalent  to  considering  the  stress-strain 
curve  to  be  represented  by  an  equation  of  the  form 


in  which  /  is  the  unit  stress,  /  the  corresponding  unit  strain  and 
K  and  M  constants.  By  taking  the  first  differential  of  this  equa- 
tion there  is  obtained 

dp 

— 
dl 

that  is,  E,  or  the  ratio  of  stress  to  strain,  is  equal  to  a  constant 
quantity,  less  the  product  of  a  different  constant,  by  the  unit  de- 
formation at  the  point  considered.  If  M  equals  zero,  the  curve 
becomes  a  straight  line  and  the  value  of  the  coefficient  constant. 
One  other  point  remains  to  be  considered  before  discussing  in 
detail  the  results  of  any  experiments,  and  has  reference  to  the 
number  of  times  a  single  load  should  be  applied  before  proceed- 
ing to  the  next  higher  load.  Professor  Bach,  for  instance,  re- 
peats his  loading  between  the  initial  load  and  the  load  in  ques- 
tion until  he  obtains  always  the  same  value  of  the  strain.  This 
involves,  in  most  cases,  removing  a  load  five  times,  and  some- 
times still  more.  Other  experimenters  apply  a  load  usually  but 
once,  and,  after  having  obtained  the  corresponding  strain,  pro- 
ceed either  to  the  next  higher  load  or  first  determine  the  set  for 
the  load  in  question.  It  appears  possible,  by  the  frequent  repe- 
tition of  loads,  to  change  the  molecular  structure  of  the  material 
so  that  it  fails  to  furnish  the  results  which  are  desired.  This  ap- 
plies particularly  to  loads  above  the  elastic  limit  for  materials 
possessing  such  limit.  As  far  as  practice  is  concerned,  however, 
in  determining  the  behavior  of  materials  in  construction,  Profes- 


74  ELASTIC  PROPERTIES  IN  GENERAL.  [Ch.  IV. 

sor  Bach's  method  seems  to  be  the  proper  procedure,  since  in 
that  case  there  is  a  constant  repetition  of  the  application  of  the 
loads;  in  practice,  however,  the  element  of  time  which  appears 
between  the  applications  of  loads  is  sufficiently  great  to  allow  the 
material  time  to  recover  completely.  This  is  not  the  case  in 
laboratory  work,  where  the  times  of  application  of  the  loads  can 
never  be  at  very  great  intervals,  although  even  there,  as  has 
been  shown,*  it  requires  but  very  little  time  for  a  cement  mix- 
ture to  be  restored  to  its  original  condition. 

Since  much  use  will  be  made  of  the  reports  of  the  Watertown 
Arsenal,  it  will  be  well  to  state  at  this  point  that  the  values  of  the 
coefficient  of  elasticity  in  the  Watertown  Arsenal  reports  were 
obtained,  in  all  cases,  by  dividing  the  difference  between  the 
initial  and  some  greater  load  by  the  difference  between  the  total 
and  permanent  deformations  for  the  loads  in  question.  In  that 
treatment  the  coefficient  was  then  assumed  to  be  a  straight  line 
between  the  initial  load  and  the  point  of  loading  considered. 
Unless  the  coefficient  is  actually  a  constant  quantity  throughout 
the  entire  range  of  loading,  every  change  of  loading  will  furnish 
a  different  value.  These  coefficients  cannot  very  well  be  called 
either  the  instantaneous  or  the  elastic  coefficients ;  but  since  they 
probably  do  not  differ  greatly  in  value  from  either,  they  will  in 
this  treatise  be  directly  compared  to  the  true  coefficients. 

Inspection  of  a  stress-strain  curve  will  determine  at  once  the 
quantities  which  express  in  numerical  figures  the  values  of  the 
usual  elastic  properties,  viz.,  the  coefficient  of  elasticity,  the  elas- 
tic limit  and  the  ultimate  resistance. 


*See  Art.  18  on  Fatigue  of  Cement  Mixtures. 


CHAPTER  V. 
TENSILE  PROPERTIES. 

Art.  20. — Coefficient  of  Elasticity  and  Ultimate  Resistance. 

A  valuable  paper  on  the  tensile  coefficient  of  elasticity  of  Port- 
land cement  mixtures  is  recorded  by  De  Joly  in  Vol.  III.,  1898, 
of  the  "Annales  des  Ponts  et  Chaussees."  His  tensile  tests  were 
conducted  on  two  sizes  of  bars,  the  first  41  inches  long  by  1x1.5 
inches  in  section,  and  the  other  47  inches  long  by  4.7x6.5  inches 
in  section.  Both  sizes  of  specimens  had  enlarged  heads  in  the 
manner  of  the  ordinary  tensile  briquette.  The  elongations,  in  all 
cases,  were  measured  on  a  gauged  length  of  39  inches.  Various 
specimens  were  made  with  different  brands  of  Portland  cements. 
Both  sizes  of  specimens  were  made  from  neat  cement,  but  con- 

TABLE  I.— SPECIMENS  OF  NEAT  CEMENT. 


No.  of 
Specimen 

Age 
in 
Days 

Coefficient  of 
Elasticity  in 
Lbs.  per  Sq.  In. 

Determined  for  a 
Tensile  Stress  of 
Lbs.  per  Sq.  In. 

Ultimate  Tensile 
Resistance  in 
Lbs.  per  Sq.  In. 

I 

28 

2  680  000 

187 

2  
2  

40 
40 

3,160,000 
3,070,000 

342 
448 

}                483 

3  

50 

3,550,000 

142 

"| 

3  

50 

3,380,000 

256 

3  

50 

3,190,000 

398 

}»              476 

3 

f)Q 

3  130  000 

455 

I 

4 

106 

4  500  000 

271 

1 

4 

106 

4  270  000 

542 

y         617 

crete  mortar  specimens  were  made  only  in  the  large  size.  The 
small  specimens  were  kept  in  fresh  water  until  the  times  of  test- 
ing, which  varied;  but  the  large  specimens  were  always  kept  in 
damp  air  until  broken;  this  was  always  thirty  days  after  making. 
Table  I.  shows  the  results  obtained  with  the  smaller  sized  bars 
and  Table  II.  some  results  on  the  larger  ones. 


76 


TENSILE  PROPERTIES. 


[Ch.  V. 


De  Joly  states  that  no  definite  point  could  be  termed  the  elastic 
limit,  but  that  it  seemed  to  be  very  near  the  point  of  rupture  for 
the  neat  cement  specimens,  and  that  it  never  fell  below  three- 
fourths  of  the  ultimate  resistance  in  the  case  of  mortars  or  con- 
cretes. De  Joly  states  that  this  does  not  seem  to  apply  to  com- 
pression tests  on  cement  mortars,  since  some  other  experiments 
made  in  the  Laboratory  de  1'Ecole  des  Fonts  et  Chaussees  show 
that  the  elastic  limit  is  well  defined  for  compression  and  its  value 
is  little  greater  than  one-half  the  ultimate  resistance.  The  coeffi- 
cients of  elasticity  as  marked  in  these  tables  are  the  true  or  elas- 
tic coefficients. 

Examination  of  these  tables  shows  that  the  coefficient  of  elas- 
ticity is  greater  for  mortars  and  concretes  than  for  neat  mixtures, 
at  least  in  the  case  of  specimens  one  month  old  and  kept  in  moist 
air.  The  coefficients  increase  with  age  in  the  case  of  neat  ce~ 

TABLE  II. 


Composition  of  Specimens  Ap- 
proximately in  Parts  by  Weight 

Cross  Section 
of  Specimen 
in  Sq.  Ins. 

Average  Value  of 
Coefficient  of  Elasticity 
in  Lbs.  per  Sq.  In. 

Average  Ultimate 
Tensile  Resistance 
in  Lbs.  per  Sq.  In. 

Cement 

Sand 

Stone 

Neat 

I 
I 

2.4 

1.3 

1.5 

31 
31 
31 

2,560,000 
3,000,000 
3,040,000 

338 
141 
135 

ments,  but  do  not  change  materially  with  the  sizes  of  the  speci- 
mens. In  another  table,  not  quoted,  De  Joly  shows  that  the 
value  of  the  coefficient  does  not  change  sensibly  for  different 
brands  of  cements ;  he  also  states  that  the  value  of  the  coefficient 
for  tension  for  any  one  neat,  mortar  or  concrete  specimen  is  con- 
stant, and,  as  compared  to  the  coefficient  of  elasticity  for  com- 
pression, is  equal,  or  greater,  but  never  less. 

The  following  series  of  tensile  tests  on  reinforced  concrete 
prisms  is  also  recorded  by  De  Joly  in  the  same  volume  of  the 
"Annales  des  Fonts  et  Chaussees"  and  is  of  exceeding  interest. 
Figure  i  shows  the  character  of  the  specimens  with  which  the 
tests  were  made.  The  specimens  of  Type  No.  I,  which  were 
both  neat,  mortar  and  concrete  mixtures,  contained  three  bars 
of  round  iron  .78  inch  in  diameter,  placed  as  shown;  all  other 
types  were  neat  cement  only.  Type  No.  II.  contained  five  bars 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE.  77 

of  iron  of  the  same  dimensions,  placed  as  shown.  Type  No.  III. 
contained  either  one  round  bar  .78  inch  in  diameter,  placed  at 
the  centre  and  continuing  throughout  the  entire  length  of  the 
concrete,  or  two  bars,  as  shown  under  the  figure  marked  Type 
III.  In  Type  No.  IV.  six  specimens  were  prepared,  each  of 
which  contained  two  bars,  also  of  the  same  diameter,  placed  sym- 


Type  IV 


P  )  ;  "1 

—^  Tvn«  TV  "JJ 


Type  IV 


Type  III 


M 

L. 


Type  II 


Type  I 


C 


FIG.  1. 

metrically  in  the  beam  and  continuing  throughout  the  entire 
length;  but  in  four  of  these  specimens  the  rods  were  fastened 
solidly  at  the  ends  by  means  of  flat  plates.  De  Joly  states  that  it 
was  impossible  to  determine  any  elastic  limit  from  the  stress- 
strain  curves  ;  it  appeared  to  be  near  the  point  of  rupture.  This 
means  that  the  apparent  coefficient  of  elasticity  is  practically  a 
constant  quantity;  it  is  calculated  by  dividing  the  unit  stress  on 
the  bar,  obtained  by  dividing  the  total  load  by  the  total  cross- 
section,  by  the  unit  deformation  of  the  bar. 

The  addition  of  metallic  reinforcement  increases  the  value  of 
the  coefficient  of  elasticity  of  a  cement  mixture,  but  this  increase 
is  never  more  than  50  per  cent.;  at  least  Table  III.  shows  this  to 
be  so  for  specimens  of  Type  No.  III. 

In  none  of  the  experiments  was  De  Joly  able  to  determine  ex- 
actly the  ultimate  resistance  of  the  reinforced  specimens.  Vari- 
ous reasons  are  given  for  this,  and  it  is  therefore  better  to  omit 
these  values. 


78 


TENSILE  PROPERTIES. 


[Ch.  V. 


The  results  given  in  Table  III.  are  each  an  average  of  one  to 
three  specimens;  in  the  case  of  the  specimens  of  Type  No.  III., 
the  spacing  apart  of  the  two  bars  is  increased  from  the  first  to  the 
fourth  tests,  there  shown,  so  that  in  the  fourth  test  the  bars  are 
very  near  the  surface  of  the  specimen.  It  will  be  seen,  then,  that 
the  coefficient  of  elasticity  increases  as  these  same  bars  vary  their 
position  within  the  specimens,  from  the  centre  to  the  outside. 
The  great  difficulty  of  making  tensile  tests  on  reinforced  concrete 
specimens  is  clearly  shown  by  the  last  statement,  which  shows 
the  unequal  distribution  of  stress  through  the  cross  section;  rea- 
soning would  tend  to  show  that  the  exterior  of  specimens  of  the 
kind  shown  carries  the  greatest  part  of  the  stress.  Reasoning 
further,  it  seems,  then,  that  iron  imbedded  in  the  very  centre  of 
concrete  specimens  will  influence  the  stress-strain  diagram  of  the 

TABLE  III. 


Specimen  of  Type 
No. 

Reinforced 
or 
Not 

When 
Stress  on 
Cross  Sec- 
tion is  Lbs. 

Coefficient  of  Elasticity  in  Lbs.  per  Sq.  In. 

Neat  Cement 

Mortar 

Concrete 

| 

No 
Yes 
No 
Yes 

2,550,000 
3,740,000 
2,560,000 
2,720,000 
3,540,000 
3,670,000 
3,820,000 
3,900,000 

3,000,000 
3,960,000 

3,030,000 

4,260,000 

I 

6160 

n  i  

III.  (with  I  bar). 
III.  (with  2  bars) 
III.  (with  2  bars) 
III.  (with  2  bars) 
III.  (with  2  bars) 



Minimum  cross  section  of  all  specimens  about  30  square  inches. 

combined  material  but  little,  and  inspection  of  Table  III.  con- 
firms this  reasoning.  It  appears,  therefore,  that  but  little  knowl- 
edge can  be  gained  of  the  elastic  behavior  of  these  two  materials 
in  combination  by  making  direct  tensile  tests  of  the  kind  indicated. 

And  these  results  are  confirmed  by  experiments  made  by  the 
author  and  recorded  in  succeeding  pages. 

W.  H.  Henby  has  recorded  in  the  Proceedings  of  the  Asso- 
ciation of  Engineering  Societies  for  September,  1900,  a  very  in- 
teresting set  of  experiments  on  the  elastic  properties  and  ulti- 
mate strength  of  stone  and  cinder  concretes  under  both  tensile 
and  compressive  stresses.  These  tests  were  made  at  Washing- 
ton University  as  thesis  work.  The  tension  specimens,  made  in 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


79 


iron  moulds,  had  a  cross  section  of  10  square  inches,  being  uni- 
formly 2^x3^-  inches  in  cross  section.  They  had  a  length  of  re- 
duced section  of  14  inches  and  an  over-all  length  of  21  inches. 
The  compression  specimens  were  made  in  wooden  moulds;  they 
had  the  same  sectional  area  as  the  tension  specimens,  with  a 

TABLE   IV. 
TENSILE  TESTS  OF  CEMENT,  MORTAR  &  STONE   CONCRETE. 


Number  of  Test] 

Age  in 
Days 

Composition 
Parts  of 

Brand 
of 
Cement 

Size  of  Broken 
Stone  in  Inches 

Treatment 

51 

i 
n 

Modulus 
of 
Elasticity 
Lbs.  per 
Sq.  In. 

Ultimate  Stress 
I.bs.  per  Sq.ln.| 

Con- 
sistency 

Remarks 

i  Cement 

I 

I 

8 

7 

1 

2 

4        L         \l/2 

Air  dry 



2,000,000  !  130 

Dry 

16 

33        1 

2 

4  i     " 

\/2 

44 

142 

2,882,000      198 

44 

17 

295 

30        1 
64     !  1 

2 

2 

4        " 
4  !     A 

2  2 

AAr 

148 
151 

4,727,000      227 
7,744,000     252 

" 

Very  dense  spec. 

315 

316 

30     i  1 

30     !  1 

2 
2 

4 
4 

2 
2 

M 

149 

148^ 

8,360,000      183 
7,280,000      214 

« 

1  Failed  in 
j  shoulder. 

22 

60     S  1 

2 

5 

1% 

Air  dry 

144 

1,857,000      111 

Very  dry 

25 

60        1 

2 

5 

44 

i» 

44 

146 

3,253,000      128 

Dry 

26 

60       1 

2 

5 

44 

i/^ 

44 

146 

3,023,000      189 

44 

30 

90       1 

2 

5 

M 

\YZ 

44 

140 

3,776,000      142 

44 

106 

90     !  1 

2 

5 

A 

\1A 

44 

144 

3,696,000      129 

Very  dry 

107 

90     |  1 

2 

5 

44 

\yz 

44 

144     !  3,896,000       93 

44 

287 

63 

1 

2 

5 

44 

2 

Air 

146 

4,980,000 

154 

Dry 

288 

63 

1 

2 

5 

44 

2 

44 

146 

3,744,000 

192 

96 

30     !  1 

3 

6 

2 

44 

150 

3,810,000 

119 

44 

271        30     1  1 

4 

8 

Water 

149 

6,108,000      125 

44 

23  !     90     ills 

-      M 

— 

Air  dry 

136 

3,988,000 

199 

44 

1  Failed  in 

24       90       13 

—       " 

— 

44 

139 

5,202,000 

234 

44 

t  shoulder. 

117      120        1 

3 

— 

— 

44 

136 

5,144,000 

144 

Very  dry 

118      120       1 

3 

— 

44 

— 

44 

136 

5,150,000 

154 

44 

18       30 

2 

4 

L 

\Vz 

44 

142 

2,269,000      191 

Plastic 

35  |     55 

2 

4 

\yz 

44 

147 

4,543,000      149 

M 

65       96     ! 

2 

4 

44 

\YZ 

44 

146 

3,992,000      190 

44 

66       96 

2 

4 

44 

\y2 

Air 

147       4,760,000 

226 

44 

72         8     | 

2 

4 

A 

1% 

44 

157       3,720,000 

213 

44 

67      100     ! 

2 

4 

L 

IH 

Air  dry 

147 

5,075,000 

209 

44 

18  |     30     1 

2 

4 

A 

2 

Air 

148 

3,306,000 

192 

44 

222       30 

2 

4 

44 

\yz 

44 

153     i  3,750,000 

223 

44 

223       30 

2 

4 

44 

t/^ 

44 

150       3,600,000 

241 

44 

224       30 

2 

4 

44 

\yz 

Water 

158 

3,550,000 

279 

44 

283       65 

2 

4 

44 

2 

Air 

144 

3,810,000 

143 

44 

Failed  in  head. 

284       65 

2 

4 

44 

2 

44 

149 

3,724,000 

102 

44 

286  !     65 

2 

4 

44 

2 

Water 

150 

5,440,000 

82 

4' 

3       14 

2 

5 

M 

\y% 

Airdry 

139 

2,000,000 

85 

44 

Not  well  ram'd. 

5       18 

2 

5 

\yz 

2,106,000 

120 

44 

78  !      7 

2 

5 

A 

ll/2 

Air 

152 

3,968,000 

147 

44 

236 

30 

2 

5 

44 

145 

4,532,000 

165 

44 

Failed  in  head. 

237 

30 

2 

5 

44 

1% 

44 

152 

4,425,000 

242 

44 

241 

30 

2 

5 

44 

\y2 

Water 

155 

5,000,000 

233 

44 

91 

7 

3 

6 

44 

\y2 

44 

154 

3,828,000 

115 

44 

242 

30 

3 

6 

44 

ig 

Ajr 

147 



130 

44 

243 

30 

3 

6 

44 

147 

2,427,006 

104 

44 

244 

30 

3 

6 

44 

\YZ 

44 

148 

2,440,000 

128 

44 

245 

30 

3 

6 

44 

\yz 

44 

144 

4,496,000 

93 

44 

270 

30 

4 

8 

44 

\YZ 

44 

143 

3,553,000 

71 

44 

235 

95 

— 

— 

M 

— 

Water 

137 

6,423,000 

645' 

44 

Failed  in  head. 

10 

18 

2 

4 

\yz 

Air  dry 

2,286,000 

75 

Excess 

36 

90 

2 

4 

44 

\yz 

44 

147 

3,500,000 

125 

44 

165 

120 

2 

4 

44 

\y2 

*4 

143 

3,473,000 

136 

44 

166 

120 

1 

2 

4 

" 

ll/2 

" 

144     i  3,473,000 

89 

A  indicates  Atlas  Brand  Cement;    M  indicates  Medusa  Brand  ;  L  indicates  Lehigh  Brand. 


80 


TENSILE  PROPERTIES. 


[Ch.  V. 


TABLE    IV '.—Continued. 
TENSILE  TESTS   OF   CINDER   CONCRETE. 


1 
j 

85 

43 
44 
46 
141 
149 
159 
155 
167 
171 
174 
132 
2 
195 
198 
202 
207 
186 
209 
212 

Age  in 
Days 

Composition 
Parts  of 

Brand 
Cement 

Size  of  Broken 
Stone  in  Inches 

Treatment 

g 

;i 

•So 

is. 

Modulus 
of 
Elasticity 
Lbs.  Per 
Sq.  in. 

Ultimate  Stress 
Lbs.  per  Sq.  In. 

Net  Ult. 
Compress. 
Resistance 
Lbs.  per 
Sq.  In. 

Remarks 

B 

1 

• 

(A 

« 
• 

tn 

4 
4 
4 
4 
4 
5 
5 
5 
5 
5 
5 
5 
6 
6 
6 
6 
6 
7 
7 

7 

7 

7 
30 
30 
30 
30 
30 
30 
30 
60 
12 
60 
60 
60 
60 
30 
30 
30 

2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
3 
3 
3 
3 

3% 
3Y2 

A 

M 
A 

Ah- 

Water 
Air 
Water 
Air 

Water 
Air 
Air^dry 

Water 
Ah- 

118 
114 
122 
113 
121 
109 
107 
102 
126 
112 
117 
113 
110 
110 
107 
108 
114 
102 
104 

1,854,000 
1,892,000 
1,826,000 
2,800,000 
2,909,000 
2,853,000 
2,329,000 
1,820,000 
1,900,000 
1,900,000 
2,413,000 
1,428,000 
1,274,000 
1,892,000 
2,215,000 
2,922,000 
1,422,000 
1,034,000 
937,000 

46 



133 
77 
86 
86 
78 
76 
129 
97 
60 
58 
88 
62 
52 
41 
30 
31 

993 
1,415 
1,039 
1,054 
688 
1,166 
1,005 
882 

699 
949 
677 

653 
409 
510 

- 



- 



- 



- 



- 

- 

A  indicates  Atlas  Brand  Cement;  M  indicates  Medusa  Brand ;  L  indicates  Lehigh  Brand. 

length  of  ii  inches.  The  deformations  were  determined  for  both 
kinds  of  stress  by  means  of  a  dial  extensometer  having  friction 
rollers  and  measuring  by  means  of  a  vernier  needle  to  .0001  of 
an  inch.  The  tensile  elongations  were  measured  on  a  gauged 
length  of  10  inches,  the  compressive  deformation  on  a  length  of 
6  inches.  Three  brands  of  Portland  cement  were  used — Atlas, 
Lehigh  and  Medusa.  The  sand  used  was  Mississippi  River  sand 
and  the  stone  was  i^  to  2  inch  limestone  macadam,  taken  in  the 
same  condition  in  which  it  came  on  the  market.  The  total  vol- 
ume of  voids  in  the  2-inch  macadam  was  57!  per  cent.;  in  the  ij- 
inch  macadam,  6if .  The  cinders  used  were  unscreened.  All  the 
measurements  were  volumetric.  It  was  found  that  the  average 
density  of  the  stone  concrete  compression  specimens  was  greater 
than  the  average  density  of  the  tensile  specimens. 

Table  IV.  shows  the  ultimate  tensile  resistance  and  the  modu- 
lus of  elasticity  of  both  stone  and  cinder  concrete  specimens;  they 
are  tabulated  in  the  order  of  their  consistency,  the  first  ones 
being  the  dry  specimens,  then  the  plastic,  then  the  excess.  From 
the  figures  accompanying  the  original  report  it  may  be  presumed 
that  the  coefficients  as  calculated  are  not  the  true  elastic  coeffi- 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


81 


cients,  since  no  permanent  deformations  or  sets  were  noted.  If 
this  be  the  case,  the  true  coefficients  would  have  higher  values, 
and  such  high  values  have  not  been  confirmed  by  other  experi- 
menters. The  results'  are  directly  comparable  in  themselves, 
however,  since  they  were  all  made  under  uniform  conditions, 
with  the  same  apparatus  and  by  the  same  experimenters;  there- 
fore, general  deductions  may  be  made. 

The  specimens  which  are  marked  ''Air"  were  covered  with 
damp  cloths;  the  others  were  either  kept  in  the  dry  air  of  the 


.00003          .00006 

Proportionate  Elongation 

FIG.  2.— HENBY'S  TESTS. 


laboratory  or  in  water,  as  marked.  Henby  concludes  that  the 
greatest  strength  is  developed  in  the  case  of  the  dry  mixtures 
in  which  ramming  is  required  to  flush  water  to  the  surface.  In 
that  case  the  density  and  the  ultimate  strength  increase  together. 
The  air  dry  specimens  show  lower  results  than  the  air  speci- 
mens, and  the  concretes  which  set  in  water  attained  greater 
strength  than  either  of  the  others.  This  does  not  appear  to  be 
the  case,  however,  for  the  cinder  concretes.  The  results  show 
that  the  coefficient  of  elasticity  increases  slightly  with  the  age  of 


82  TENSILE  PROPERTIES.  [Ch.  V. 

the  specimen,  and  perhaps  slightly  with  the  denseness  of  the 
mixture.  This  is  equivalent  to  saying  that  the  coefficient  in- 
creases with  the  ultimate  resistance. 

Table  IV.  also  gives  tensile  results  found  with  cinder  concretes. 
It  will  be  seen  that  the  ultimate  tensile  resistances  are  very  low, 
averaging  perhaps  75  pounds  per  square  inch.  The  coefficients 
of  elasticity  are  also  lower  than  in  the  case  of  the  stone  concrete 
specimens  and  they  decrease  with  the  leanness  of  the  mixtures. 

Figure  2  is  taken  from  Mr.  Henby's  paper  and  shows  the  char- 
acteristic stress-strain  curves  for  seven  tension  tests  of  1:2:4 
stone  concretes.  An  elastic  limit  might  be  placed  at  about  two- 
thirds  of  the  ultimate  resistance. 

In  some  other  tensile  experiments,  not  here  tabulated,  Henby 
found  that  some  cinder  concrete  specimens  thirty-three  days  old, 
one  part  Atlas  cement,  three  sand  and  six  cinder,  gave  an  aver- 
age value  of  the  coefficient  for  dry  specimens  of  2,368,000,  and 
for  wet  specimens  of  898,000  Ibs.  per  sq.  in.  It  will  be  seen  that 
the  dry  specimens  are  much  more  resistent  to  deformation  than 
the  wet. 

Henby  also  made  the  following  experiments  on  eight  cinder 
concrete  specimens  of  the  tensile  form.  All  the  specimens  were 
first  set  in  damp  cloths  for  forty-eight  hours  and  were  then  kept, 
in  dry  air  for  twenty-eight  days.  Half  of  the  batch  were  then 
put  in  water  for  three  days.  The  average  tensile  resistance  of 
the  four  dry  specimens  was  found  to  be  89  pounds  per  square 
inch,  and  of  the  four  wet  specimens,  46  pounds  per  square  inch. 
One  "half  of  the  halves  of  the  dry  tensile  specimens  were  then 
immediately  tested  to  failure  by  compression;  the  other  half  were 
tested  after  being  in  water  forty-eight  hours.  Also,  half  of  the 
halves  of  the  wet  specimens  were  tested  immediately  and  the 
other  half  were  dried  at  125  degrees  Fahr.  for  forty-eight  hours 
before  being  broken.  The  four  specimens  which  had  never  been 
in  water  averaged  827  pounds  per  square  inch;  the  eight  wet 
specimens,  734  pounds  per  square  inch,  and  the  four  dry  speci- 
mens broken  after  having  been  dried  averaged  1,008  pounds  per 
square  inch. 

It  will  be  seen,  then,  that  these  specimens  when  tested  wet  de- 


Art.  20.]    COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


83 


veloped  less  strength  than  when  tested  dry,  but  surpassed  the  dry 
specimens  after  having  been  dried. 

Table  V.  is  taken  from  a  paper  read  before  the  American  Sec- 
tion of  the  International  Association  for  Testing  Materials  by 
Professor  W.  K.  Hatt  at  the  annual  meeting,  1902,  and  shows 
the  values  of  the  tensile  coefficient  of  elasticity  of  concrete  bars. 

TABLE  V. 


Number  of  Bar 

Age  in  Days 

Coefficient  of  Elasticity 
in  Lbs.  per  Sq.  In. 

Ultimate  Tensile  Strength 
in  Lbs.  per  Sq.  In. 

I  

35 

2  700  000 

300 

2  

33 

2  400  000 

30"S 

3  

28 

I  400  000 

360 

4 

26 

I  900  000 

9  on 

The  size  of  the  specimens  was  4x4  inches  square,  and  the  elonga- 
tions were  measured  on  a  length  of  17^  inches,  although  the 
specimens  were  about  30  inches  long.  The  values  of  the  ulti- 
mate strength  as  given  are  not  very  satisfactory,  as  many  of  tlie 
bars  broke  in  the  head;  but  Professor  Hatt  believes  that  the 
strength  of  the  body  of  the  bars  was  not  different  from  the  loads 
recorded  at  the  point  of  rupture  of  the  heads.  The  mixture  was 

TABLE   VI. 


Number 
of  Bar 

Composition 

Age 
in 
Days 

Compressive 
Coefficient  of 
Elasticity  in 
Lbs.  per  Sq.  In. 

Determined 
At  a  Compressive 
Stress  of 
Lbs.  per  Sq.  In. 

Ultimate 
Crushing 
Strength  in 
Lbs.  per  Sq.  In. 

I  

:2:4  Stone  .  .  . 

9 

4  702  000 

750 

IftftO 

1 

'2'4  Stone 

q 

3  940  ooo 

I5OO 

Oftftrt 

2 

•2*4  Stone 

14 

4  340  000 

750 

0^7^ 

2 

•2*4  Stone 

14 

3  680  000 

1500 

^5/p 
9tS7B> 

3  

•2*4  Cinder 

9 

558  600 

*J'J 

ACtZ, 

4  

•2:4  Cinder.  . 

9 

553  000 

5Qt 

5  

:2:4  Cinder.  . 

7 

630  000 

JJJ 
416 

6 

6 

2  088  000 

I  I  A^ 

composed  of  I  part  Peninsular  Portland  cement  and  2  parts  of 
clean,  sharp  pit  sand,  of  which  84  per  cent,  was  retained  on  a 
Xo.  30  sieve,  and  4  parts  of  broken  limestone,  all  of  which  passed 
through  a  one-inch  sieve  and  of  which  75  per  cent,  was  retained 
on  a  ^-inch  sieve. 

The  coefficient  of  elasticity  was  computed  with  regard  to  the 


84 


TENSILE  PROPERTIES. 


[Ch.  V. 


set  experienced  after  previous  loads;  in  other  words,  it  is  the 
"elastic"  modulus  of  elasticity. 

Table  VI.  furnishes  values  of  the  compressive  coefficient  of 
elasticity  for  concrete  cylinders  12  inches  high  and  8  inches  in 
diameter,  also  reported  by  Professor  Hatt  in  the  same  paper. 

In  addition  to  the  concrete  mixture  noted  above,  tests  were 
made  on  a  1:2:4  cinder  concrete  and  a  1 15  gravel  concrete,  the 
gravel  being  a  good  quality  of  coarse  gravel.  The  intensity  of 
stress  at  which  the  compressive  coefficient  of  elasticity  was  com- 
puted is  shown  in  the  table. 

These  experiments  show  the  coefficient  for  compression  to  be 
considerably  larger  than  for  tension,  but  Professor  Hatt  has 
lately  (Western  Society  of  Engineers,  1904,)  published  the  re- 
sults of  a  greater  number  of  tests,  and  he  states  definitely  that  he 
finds  no  appreciable  difference  between  the  two  moduli.  Table 
VII.,  taken  from  the  latter  paper,  is  otherwise  self-explanatory; 

TABLE  VII. 


Kind  of  Concrete.—  Parts  of 

Age 
in 
Days 

Coefficient  of  Elasticity 
in  Lbs.  per  Sq    In. 

Ultimate  Strength 
in  Lbs.  per  Sq.  In. 

Cement 

Sand 

Broken 
Stone 

Gravel 

Com- 
pression 

Tension 

Com- 
pression 

Tension 

I 
I 
I 

I 

2 

in  in 

5 

90 

28 
90 
28 

4,610,000 
3,350,000 
4,800,000 
4,130,000 

5,460,000 
3,800,000 
4,510,000 
4,320,000 

2413 
2290 
2804 
2405 

359 
237 
290 
253 

the  results  being  averages  of  thirty-seven  compression  and  twen- 
ty-seven tension  specimens;  the  broken  stone  was  limestone, 
being  the  product  of  the  crusher  below  i  inch,  and  the  gravel  ex- 
cellent pit  gravel,  including  sand  and  pebbles.  The  concrete  was 
mixed  medium  wet. 

The  following  tests  on  the  tensile  strength  and  the  tensile  co- 
efficient of  elasticity  of  concrete  were  made  in  the  Mechanical 
Laboratory  of  the  Department  of  Civil  Engineering  of  Columbia 
University  under  the  author's  supervision  by  Walter  T.  Derleth 
and  John  Hawkesworth,  graduating  students  of  the  fourth  class 
in  civil  engineering.  The  work  was  begun  early  in  1903  and 
lasted  until  the  first  part  of  June,  1904.  The  cement  which  was 


Art.  20.]    COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE.  85 

used  was  Atlas  Portland,  upon  which  the  usual  acceptance  tests 
were  made. 

As  determined  by  the  Gillmore  needle,  the  initial  set  took  place 
in  i  hour  and  45  minutes,  and  the  final  set  in  3  hours  and  50 
minutes.  The  strength  of  the  neat  cement  briquettes,  gauged 
with  13  per  cent,  of  water,  averaged  508  pounds  per  square  inch 
at  the  end  of  48  hours,  595  pounds  per  square  inch  at  the  end  of 
7  days,  and  849  pounds  per  square  inch  at  the  end  of  28  days. 
Mortar  briquettes  of  one  cement  to  one  normal  sand,  gauged 
with  11.3  per  cent,  of  water,  averaged  583  pounds  per  square 
inch  at  the  end  of  7  days  and  671  pounds  per  square  inch  at  the 
end  of  28  days.  Mortar  briquettes,  one  cement  to  three  normal 
sand,  gauged  with  about  8  per  cent,  of  water,  averaged  148 
pounds  per  square  inch  at  the  end  of  7  days  and  203  pounds  per 
square  inch  at  the  end  of  28  days. 

The  sand  which  was  used  in  making  the  concrete  was  Cow 
Bay,  and  was  clean  and  sharp.  Its  fineness,  as  tested  by  stand- 
ard sieves,  was  as  follows: 

Retained  by  No.     2  sieve 0.49% 

*     "      3      "    1.15% 

"     "      4     "    6.68% 

"        "      20       "      9.52% 

"        "      30       "      15-55% 

"        "      50        "      38.90% 

Passed       "      "     50      "    27.7% 

The  percentage  of  voids  in  the  sand  was  determined  to  be  40.5 
per  cent.  The  stone  which  was  used  for  the  concrete  was  a  blue 
limestone,  broken  into  sharp,  angular  pieces,  varying  in  dimen- 
sions from  3  inches  to  J  inch.  The  percentage  of  voids,  deter- 
mined by  an  average  of  two  tests,  was  48.1  per  cent.  All  the 
concrete  for  the  tests  was  composed  of  one  part  of  cement  to 
three  parts  of  sand  and  five  parts  of  broken  stone,  by  volume; 
and  these  ratios  by  volume  correspond  very  closely  to  the  actual 
weights  of  the  different  constituents  used  in  the  mixture.  Each 
specimen  or  bar  contained  about  ij  cubic  feet  of  concrete,  and 
each  was  prepared  separately  from  a  batch  of  the  materials 


86  TENSILE  PROPERTIES.  [Ch.  V. 

which  averaged  about  ij  cubic  feet.  The  sand  and  cement  were 
first  thoroughly  mixed  dry  and  then  the  moistened  broken  stone 
was  added,  the  whole  being  turned  several  times  before  the  ad- 
dition of  water.  Water  was  then  slowly  added  while  the  ma- 
terial was  being  turned  over  by  shovels  until  its  consistency  was 
very  plastic.  The  concrete  was  then  deposited  in  the  wooden 
moulds  and  lightly  rammed  into  place  with  a  wooden  rod.  After 
the  first  five  bars  had  been  moulded,  it  was  found  better  to  make 
the  mixture  so  fluid  that  very  little  tamping  was  necessary;  its 
consistency  was  then  what  is  known  as  "very  wet  concrete." 

The  moulds  were  always  well  moistened,  and  also  greased  with 
soft  soap,  before  depositing  the  concrete,  and  no  trouble  was 
experienced  in  removing  the  bars  from  the  moulds.  The  pins 
were  covered  with  paraffined  paper,  so  that  they  were  easily 
withdrawn  after  the  specimen  had  set.  It  was  found  imprac- 
ticable to  remove  the  specimens  from  the  moulds  before  four  or 
five  days.  Specimens  Nos.  2,  3  and  4  broke  during  the  manu- 
facture, due  to  improper  handling  or  too  early  removal  from  the 
moulds.  In  order  to  strengthen  the  heads  of  the  specimens  in 
the  neighborhood  of  the  pins  through  which  the  tensile  pressure 
was  later  applied  looped  pieces  of  iron  telegraph  wire  or  heavy- 
weight picture  wire  were  inserted. 

The  shape  of  the  specimens  is  clearly  shown  in  the  following 
figure,  the  cross  section  of  each  piece  being  6x6  inches  and  the 
diameter  of  the  pin  hole  through  the  head  being  if  inches. 


Pin  hole  1^diain. 


FIG.  3. 

For  the  purpose  of  measuring  the  stretch  or  decrease  in  length 
of  these  specimens,  upon  the  application  of  loads,  it  was  neces- 
sary to  have  built  a  special  extensometer.  This  piece  of  appara- 
tus was  made  by  T.  Olsen  &  Co.  of  Philadelphia,  and  consisted 
of  two  frames  which  inclosed  the  specimen  and  which  were 
firmly  fastened  to  it  at  a  distance  apart  of  25  inches ;  on  opposite 


Showing  Method  of  Determining  the  Elastic  Behavior  of  Concrete  Bars,  6x6-Inches  in  Cross-Section,  the 
Specimens,  with  Electric  Extensometer  Attached,  being  Mounted  for  Tension  Experiments  in  the 
150,000  Pound  Emery  Testing  Machine  of  Columbia  University.  In  the  Photographs,  as  Shown, 
the  Test-Pieces  Are  Blocked  Up  with  Wooden  Wedges.  The  First  Specimens  Tested  Were  Hung 
from  Heavy  Steel  Cables,  with  Looped  Eyes,  but  a  Second,  and  Better  Method  of  Attachment,  by 
Means  of  Parallel  Side  Plates,  is  Shown  in  the  Right-Hand  Figure.  Enlarged  Views  of  the  Heads  of 
the  Specimens  Are  Shown  Opposite  Page  120. 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE.  87 

sides  of  the  tipper  frame  were  fastened  two  brass  rods  held  in 
ball-and-socket  joints;  by  means  of  micrometer  screws  these 
made  electrical  contact  with  two  contact  plates,  which  were  in 
turn  fastenend  to  the  lower  frame.  Two  rods,  one  on  each  side 
of  the  specimen,  were  used  in  order  to  guard  against  errors  of 
observation  and  to  eliminate  errors  due  to  bending  cf  the  speci- 
men. The  micrometer  screws  had  a  pitch  of  1-40  of  an  inch,  and 

\ 


•H  t 


FIG.  4. 

the  micrometer  head  was  divided  into  250  parts,  so  that  each 
division  of  the  head  represented  .0001  of  an  inch.  It  was  found 
impracticable  to  measure  smaller  parts  than  one  division  of  the 
head.  The  accuracy  of  the  screws  was  tested  by  means, of  a 
dividing  engine  in  the  laboratory  of  the  Physics  Department  of 
Columbia  University,  and  was  found  to  be  exact  for  the  range  of 
testing  for  which  the  instrument  was  designed. 

Tests  were  also  made  upon  concrete  bars  of  the  same  form 
which  were  reinforced  by  wrought-iron  bars,  and  it  will  be  con- 
v-enient  to  record  at  this  point  the  results  of  tests  made  upon 
these  wrought-iron  bars. 

Three  bars  were  tested — one  f  of  an  inch  square,  which  de- 
veloped an  ultimate  resistance  of  48,700  pounds  per  square  inch, 
with  a  coefficient  of  elasticity  of  29,620,000;  one  bar  ^  inch 
square  showed  an  ultimate  resistance  of  54,800  pounds  per 
square  inch  and  a  coefficient  of  elasticity  of  29,900,000,  and  one 
bar  f  of  an  inch  square  had  an  ultimate  resistance  of  52,275 
pounds  per  square  inch  and  a  coefficient  of  elasticity  of  27,- 
590,000. 

Failure  of  the  specimens,  in  the  tensile  tests,  occurred  in  ail 
cases  but  two,  in  the  head,  on  each  side  of  the  pin  hole.  The 
wires  imbedded  in  the  head  were  not  broken,  but  had  slipped 


88 


TENSILE  PROPERTIES. 


[Ch.  V, 


in  the  concrete.  The  ultimate  tensile  resistances  are  therefore 
not  of  any  value;  the  stress  conditions  at  the  pins  in  members  of 
this  shape  are  so  peculiar  that  in  future  it  will  be  well  to  devise 
some  other  method  of  applying  the  stress  than  the  one  which  was 
used.  In  the  compression  tests  none  of  the  specimens  was 


Load 
pe: 

in  Ibs. 
sq.in. 

c 

A 

H 

J 

fl1"*      -^4 

i 

1 

| 

/1  50 

J  |ioo 

Sp< 

Ag 

ciinei 

:  138  c 

No.  5 
ays. 

Pla 
Lengt 
Sectio 

n  Con 
i       :6 

jrete 

/      1150 

Area 
Areas 

tPuy-324/5G/' 

»f        200 

Ult 

Rests 

.,  Boc 
Pin 

y  876  Ibs.per  sq.in. 

1000      " 

I  L 

Elastic  L 

Load 
Ibs.per  sq.in 
0-300 
300  -  500 

unit 

\     \ 

J 

" 

a 
o 

g 

.  Coel 

icient|of  Elasticity 
2860000  Ibs.  per  sq.ir 
2665000      «         u 

m 

350 

£ 

500-60 

i 

25000 

00     << 

J/ll 

i 

400 

X 

!"§ 

1 

450 

/ 

1 

1 

500 

/  / 

8 

1 

550 

/ 

1 

/ 

600 

FIG.  5. 


stressed  to  such  an  extent  as  to  cause  failure  in  the  body  of  the 
bar;  failure  occurred  generally  by  crushing  or  shearing  at  the 
heads  or  at  the  pin  holes,  but  was  usually  accompanied  by  fine 
cracks  appearing  generally  over  the  entire  surface,  so  that  the 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


89 


FIG.  6. 


ultimate  resistance  was  very  nearly  developed.  None  of  these 
considerations  concerning  methods  of  failure  disturbs,  however, 
the  measurements  of  the  elastic  deformations.  It  should  be 


90 


TENSILE  PROPERTIES. 


[Ch.  V. 


Load 
per 

in  Ibs. 
sq.in. 

Age: 

125  da 

-s. 

50 

Coeffi 

Ult.K 

cient  i 

esist., 
a 
f  Bias 

Body 
t  Pin 
ticity 

33  lbs.per  sq.in, 
1154000  Ibs.  per  sq.in 

40 

j  

30 

1 

/ 
/ 

J 

6 

H 

20 

t 

7 

10 

ll\ 

/ 

i 

1 

| 

i 

1 

I 

1 

i 

i 

\P/ 

Id 

§d 

j\5Q     ^ 

i. 

i 

I 

I1 

p  jioo 

i 

Sp 
Ag 

^cimei1 
i:  133  e 

No.  8 
ays. 

Plain  Con 
Length 
Section 

crete 

w; 

6x65 

i" 

/  !*> 

Area 
Area  at  Pin 

37  H  a" 
32VSQ// 

/ 

Ll 

200 

Ult.B 
E 

esist., 
astic  i 

Body 
tPin 
Jmit 

686  Ibs.  per  sq.in. 
'785      "          «« 
450      <t           u 

// 

250 

JE 
Ibs.p 

oad 

er  sq. 

n. 

Coefl 

| 

^cient  pf  Ela 

iticity 

/ 

// 

/ 

300 

| 

0- 
300- 
600- 

300 
500 
600 

1910000  Ibs.  per  sq.in.  / 
1900000       a         u     /*• 
1667000        ><          «  / 

> 

/ 

/ 

s/ 

350 

I 

J 
It 

U 

/  j 

£ 

7 

400 

5 

// 

s/ 
PI 

It 

| 

450 

.// 

/ 

^7 
/ 

// 

500 

* 

/ 

/ 
§/ 

/ 

I 

550 

X 

/ 

/ 
/ 
/ 

/ 

600 



FIG.  7. 


noted,  however,  that  both  kinds  of  stress,  tension  and  compres- 
sion, were  applied,  in  the  order  named,  to  every  individual  speci- 
men. This  was  done  in  order  to  eliminate  from  the  results  any 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


91 


possibility  of  differences  in  the  method  of  manufacture  of  the 
specimens,  and  that  the  elastic  properties  of  the  two  kinds  of 
stress  might  be  directly  compared.  An  objection  might  there- 
fore be  lodged  against  the  compression  tests,  since  these  suc- 
ceeded the  tension  tests;  but,  in  the  opinion  of  the  author,  none 
of  the  specimens  was  injuriously  affected  by  the  previous  tests, 
principally  because  the  tension  tests  failed  at  such  low  intensities. 
Table  VIII. ,  page  95,  records  the  results  of  these  experiments. 

After  each  whole  specimen  had  been  subjected  to  the  com- 
pression test,  parts  of  the  same  were  then  subjected  to  crushing 


Ult  Resis 


Age: 


e:  124  days. 


Specimen  No.  9 


31  daj  s. 


Ult.Resist., 
Elastic  Linlit 


n  Ibs. 
per  sq.in. 


.,  Body  29  lbs.per_sq.in. 
at  Pin  33     »       •«. 


f  Elasticity  13150001 


Length 
Section 


Aitaa  at  I 


Body: 
Pin 


Load|lbs.p.sq.in. 
0-  200 

I 


Concr  !te 


per  sq.in. 


Icient  of 
1800000 


*l 


Elasticity 
Lbs.per  sq.i 


FIG.  8. 

and  to  shearing  tests.  The  manner  of  loading  in  the  latter  case 
is  shown  in  Figure  4,  page  87. 

It  is  the  opinion  of  the  author  that  the  size  of  broken  stone 
used  in  these  tests  was  too  large.  In  bars  6x6  inches  in  section 
3  inch  stone  is  too  large;  it  would  have  been  preferable  if  2,  inch 
stone  had  been  the  limiting  size. 

The  stress-strain  curves  for  specimens  Nos.  5,  6,  8,  9,  n,  22 


92 


TENSILE  PROPERTIES. 


[Ch.  V. 


and  23  are  shown  in  Figures  5  to  1 1  respectively ;  it  will  be  seen 
that  the  curves  for  tension  and  compression  are  very  nearly 
straight  lines,  with  equal  inclinations. 

Table  IX.,  page  96,  shows  the  results  of  tests  made  in  the 
Laboratory  of  the  Technical  Institute  of  Vienna  during  1891  and 
1892,  and  are  recorded  in  the  Transactions  of  the  Austrian  Soci- 
ety of  Civil  Engineers  for  1895. 


1 

Load 
per 

in  Ibs. 
sq.in. 

10 

U 

ge:  120|days. 
It.Resikt.,  Bi 

>dy  33 
•in    38 

Ibs.  per. 

sq.in. 

30 

s 

C( 

efficie 

it  of  E 

astic 

ty    133 

WOO  Ib 

s.  per  s 

a.m. 

M 

\   , 
1  I 

/ 

2 
3 
H 

10 

'  / 

/•// 

I 

1 

| 

1 

i 

I 

I 

1 

1 

Jd 

I'S 

/l»     * 

i 

i 

1 

i1 

Sp< 

Agt 

cimen 
:  123  ds 

No.  1 

ys. 

PI, 

Leng 
Sect! 

,in  Coi 
;h 

t>n 

crete 

25;; 

6x6: 

•" 

/i- 

i 

Area! 
Area  kit  Pin 

36%  °" 
32k,o=' 

I 

150 

§ 

Ult.R 

esist., 

3ody 
Pin 

728  Ibs 
832  - 

per  sq. 

n. 

/  / 
/  / 

'I 

200 

1 

Ibs 

Load 

per  sq. 

In. 

Coefl 

icient 

)f  Elai 

ticity 

a 

1 

250 

5 

0- 

300 

1666000 

/ 

i 
i 

/ 

» 

350 

FIG.  9. 

The  batch  numbers  marked  Wa  were  left  in  water  three 
months  from  the  day  of  making,  being  removed  three  days  be- 
fore the  test;  batch  numbers  marked  Wb  were  left  in  water  the 
entire  time. 

The  table  gives  the  ultimate  compressive  resistance  of  4  inch 
cubes  and  of  3^x3^x10  inch  prisms.  The  strains  experienced  by 
the  latter  were  also  measured,  so  that  it  was  possible  to  obtain 
values  of  the  coefficient  of  elasticity.  The  table  also  gives  values 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


93 


Load 
per 

in  Ibs. 
sq.in. 

Age: 

111  da 

rs. 

50 

1 

Ult.Resist., 

Body 
Pin 

•43  Ibs.] 
19  _   » 

jer  sq.ii 

? 

40 

/ 

/ 

2 

3 

Coeffi 

cient 

jrf  Elas 

ticity 

8800001 

bs.  per 

sq.in. 

30 

/ 

/ 

/ 

/ 

X 

1 

20 

i 

// 

/ 

5 

10 

//; 

/ 

s~ 

PI 

1 

i 

i 

I 

i 

1 

i 

i 

w 

a*  5 

i 

I 

i 

Sp 

Ag 

jciiner 
i:  117  d 

.No.  2 
ays. 

2       Plain  Co 
Length 
Section 

acrete 
25// 
6x6! 

(" 

/ 

100 

Area  | 
Area  at  Pin 

38M^' 
32Hy/ 

/ 

150 

UU.B 
E 

esist., 
astic 

Body 
Pin 

Limit 

537  Ibs.  per  sq.in, 
612       " 
400       " 

200 

,      Lo 

Ibspei 

id- 

sq.in; 

Coef 

icient 

of  Ela 

iticity 

/ 

260 

0- 
300- 

300 
500 

1390000  lbs.per  sq.in.        / 
•1258000                  «          / 

, 

/ 

/ 

300 

s 

'/ 

// 

/ 

350 

1 

o. 

/  , 

/ 
/ 

100 

0 

x 

x 

/ 
/ 
/ 
/ 

y 

: 

150 

/ 

X 

/ 
/ 

x 

/ 
/ 

500 

"^ 

/ 

/ 

560 

600 

FIG.   10. 


of  the  ultimate  resistance  and  the  coefficient  of  elasticity  of  con- 
crete and  mortar  specimens  in  tension.  It  was  found  that  the 
concrete  prisms  had  permanent  sets  at  relatively  low  stresses. 


94 


TENSILE  PROPERTIES. 


[Ch.  V. 


p 

\  Load 
in  Lbs. 
r_sq._iij 

Age: 
Ult.  I 

112  days 
lesist.,|Body 

59  Ib 
67 
17  ICO 

s.per  sq.in. 

1 

y 

Coeffi 

cient  ( 

)f.Elas 

ticity 

1)0  Ibs.j 

>er  sq. 

n. 

10  ' 

f 

/f 

n 

a 

0) 

•// 

Jc 

l 

ill 

i  i 

|     ! 

i    i 

1 

I 

! 

i 

:    i 

1 

1      1       I 

0 

/ 

100 

/ 

.. 

- 

Specmen 

-Age-:-l-).S-l 

23     P 

ainCc 

ncrett 

! 

200 

Length        25  Ins. 
Section       6?x  6%" 
Area            38M  •=  " 

// 

Ulll  Resii 

t.,  Bo 

ly  561 
—651 
325 

Area, 
bs.per 

Pin  3 
sq.in. 

*/ 

J/ 

/L 

0 

Elastic  Limit 
Load 

/ 

/ 

350 

O 

I 

Ibs.per  sq.in.  Coefficient  of 
Elasticity       / 
0-300      1800000'lbs.per'Sq.In.X 

^   / 

f 

i 

Uoo 

3 
o 
0 

300-50JO 

910000 

/* 

7 

/ 

/ 

L 

^^Z. 

^ 

^ 

,. 

/ 

/ 

L 

^" 

550 

600 

FIG.  11. 


The  report  states  that  the  total  strain  in  both  tension  and  com- 
pression was  nearly  always  proportional  to  the  loadings,  but  that 
this  cannot  be  set  down  as  a  rule.  Nor  could  the  tests  decide 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


95 


ko  ko  ko  I-H  •— 

OJkOH-ii-.O 


?  ?  ? 

nnn 


n 


:  o    :  o  o  o 

CL         CL  D.  d. 


„  3 

KD 

/=0 

:a 


vjvjj'-'Oo  I  oo  oo  ko  I    cr\ 


a>M  ?  5'S)  S 

la^t-ga 

§5tsr§I 

3     Sn 


O  ^o 

o^  ui 

00 


oo  CD  vj  oo 
-fk  CT\  00  OJ 


rf 

Slo 


00  1-1  U* 

O  O  —•  O        VJT  ji. 


I     00     I 

1        i.     ' 


kO       <->   kJ  Oi 
VO      \Q  ^Q   •-> 


ON  OS   I    OB 

vjn  •-•        oo 
>-|  kO    I     kO 


4XI-.  1-1  \Q   \Q  00 

i— i  ^jt  i— i  v<3  oo  vj 

P  C^  >•*  «  H-I  00 

O  O  O  O  O  O 


HI  «          1-1          i-.  «  kO  kO 

)  >vO  O  CD 

>  o  o  o 


wo      >-.      \£>  ,-, 


O  H-I  >-•  O  VO 

O  O  O  O  O 

O  O  O  O  O 

o  o  o  o  o 


P  00 


K-l     H-<     kO 

p  p  u> 

o  o  o 
o  o  o 

000 


ko  v>o     i— i 


<->  00 

^o  ^o 
p  c> 

o  o 

o  o 
o  o 


Of  6  Inch 
Cube  in 
Lbs.  per 
Sq.  Inch 


I     I 


I     I 


I     i 


I     I 


At  Age  of 
Days 


_  _    _  ^0 

Ut        00  CN  — 
'     00    '     vJCN4^ 


In  Lbs. 
per  Sq.In. 


I  I  I  I  I   I   I  I  I  I 


«  «   .     .  » 
ko  ko          vji 

oo  oo  '    '  -i 


»M  .   M  »^  M  M  {  At  Age  of 


2?. 

si  5 


96 


TENSILE  PROPERTIES. 


[Ch.  V. 


, 

•ui  *b§  jad  -sqq 

A-JIDIJSB[3JOJU3IO 
•!JJ3OD  33«J3Ay 

lil  11  i  II  ii 

o 
55 
55 

•ui  'b§  J3d  -sqq 

Ul  30UBJSIS3JI 
•JJQ    33BJ3AV 

t^*   ^"  O               ^N  00                   ^"  ^-  *                   r^    "^                  C^N  vTN 

u 

H 

sqjuow  ui  33y 

===  u«  --  --  — 

SU3UIp3d§ 

—  «-  —  «-  »« 

i 
1 

.c 

•ui  'bg  J3d  -sqq 

A"JIOIJSB[3  JOJU3IO 

ooo         o                   o           oo           oo 

^"  co  1^            O                           CO              t^  tx               *"-  \& 

C 

o 

X 

•ui  "bg  J3d  'sqq 

UI  30UBJSIS3JI 
•JIQ  33BJ3AV 

00'^"'—'            co»n              ir\O               G^  CO              «r\fS 

ir>  co  co         oo  co           in  r%            in  cs            ^  t^ 
ootx         v^oo           i>«in           oo^           oo  >—  i 

COCSCN                    i—  i                 COCO                CSCO                C^CO 

no 

X 

»„„„„»,  «v 

"^f  ^  -^-          coco             co                  coco             coco 

O 

CO 

,So"^NS 

cococo        •-»  •->           r»»-«           r*-—           TTCO 

M 

flu 

XJIABJQ  oijioads 

•^•\OOO            JNCO              OcO              CS^*              i—  ii—  i 
(NCS<N            —  '  <N               i-ico              fSCS               co  co 

0 

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UI  30UBJSIS3^ 
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COCNC^              —  '  C*                  COCO                 C<CO                 COCO 

</> 

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sqjuoiv  ui  33y 

•f  "*•  ^f          coco            coco            coco            -co 

1 

(A 

« 

FSSS& 

«-«     «-      «-      —       *« 

r* 

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o 

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-==  -f  -f  -f  -5 

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S 

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<3              ...           ...            ...                   w 

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i-1    ^               d  *^    Zi           d  "^    i^         G  ^    Zi               d  ^ 

cc         cc.S       GC.G       GC-G         E^ 
--co         —  co  vn       —  <N  co       •—>-»«          •—  co 

0 

c 

o 

.\BKAtfy- 
OF  THE 

UNIVERSITY 


Art.  20.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE.  97 

definitely  whether  the  coefficient  of  elasticity  for  tension  or  com- 
pression differed.  It  will  be  seen  in  these  experiments  that  the 
values  of  the  coefficients  of  elasticity  decrease  as  the  proportions 
of  other  materials  to  sand  increase,  and  that  as  the  ultimate 
strength  of  the  mixture  increases  so  does  the  coefficient  of  elas- 
ticity. It  is  not  clearly  stated  whether  the  values  are  the  elastic 
values  of  the  coefficients;  it  must  be  so  inferred. 


Tensile  Properties. 

Conclusions. 

From  the  foregoing  experiments  it  is  possible  to  draw  the  fol- 
lowing conclusions : 

First.  Concrete  in  tension  appears  to  possess  no  point  which 
might  be  termed  the  elastic  limit;  in  other  words,  the  coefficient 
of  elasticity  is  a  constant  quantity  from  a  condition  of  no  stress 
to  the  point  of  rupture. 

Second.  The  coefficient  of  elasticity  appears  to  increase  with 
the  ultimate  tensile  strength  of  the  material,  but,  due  to  the  great 
difficulty  in  determining  the  actual  breaking  loads  of  concrete 
bars  in  tension,  it  seems  impossible  to  connect  in  any  rational 
manner  the  coefficients  with  the  breaking  loads. 

Third.  The  ultimate  tensile  resistance  varies  in  some  manner 
with  the  richness  of  the  mixture  and  with  the  age  of  the  speci- 
men, but  it  appears  impossible  to  determine  any  expression  which 
will  present  rationally  the  relation  of  these  quantities  to  one 
another. 

It  is  only  possible  to  say  that  the  value  of  the  elastic  or  true 
coefficient  of  elasticity  has  been  found  to  vary  between  1,000,000 
and  5,000,000  pounds  per  square  inch,  and  that  the  ultimate  ten- 
sile resistance  varies  from  100  to  500  pounds  per  square  inch. 

It  will  be  seen  later  that  it  appears  possible  to  connect  the 
ultimate  crushing  resistance  of  concrete  with  the  compressive  co- 
efficient of  elasticity,  and  since  it  has  previously  been  shown  that 
the  ratio  between  ultimate  tensile  and  compressive  resistance  is 
about  as  1:10,  it  may  be  possible  to  transpose  to  tension  the 
empiric  relations  deduced  in  the  compression  experiments  by  in- 


98  TENSILE  PROPERTIES.  [Ch.  V. 

serting  in  those  expressions,  in  the  proper  manner,  the  ratio  of 
i  to  10. 

From  the  experiments  that  have  been  recorded  so  far,  and 
from  those  which  will  be  shown  for  compression,  it  may  be  said 
without  much  error  that  the  coefficients  for  both  tension  and 
compression  for  any  one  mixture  may  always  be  taken  equal. 
This  will  indicate  the  manner  in  which  the  ratio  of  i  to  10  must 
be  used. 


CHAPTER  VI. 

COMPRESSIVE  PROPERTIES. 

Art.  21. — Coefficient  of  Elasticity  and  Ultimate  Resistance. 

Professor  C.  Bach  of  Stuttgart  has  made  perhaps  the  most  in- 
teresting and  most  reliable  of  experiments  on  the  compressive 
elasticity  of  cement  and  cement  mixtures.  His  experiments  on 
the  elasticity  of  concrete  have  been  published  in  the  "Zeitschrift 
des  Vereines  Deutscher  Ingenieure"  for  April  27,  1895,  and  No- 
vember 28,  1896. 

The  experiments  recorded  in  the  first  issue  mentioned  were 
made  by  Professor  Bach  in  July,  1894,  on  32  cylinders  with  a 
circular  cross  section  having  a  diameter  of  9.9  inches  and  a 
height  of  39.4  inches.  Six  different  proportions  of  ingredients 
were  used,  and  in  general  six  specimens  were  made  of  each  mix- 
ture, three  with  one  brand  of  cement  and  three  with  another 
brand.  The  following  table  shows  the  mixtures  employed,  the 
parts  being  expressed  by  volume: 

I.  i  cement,  2.\  Neckar  sand,  5  Neckar  gravel. 

II.        cement,  2.\  Neckar  sand,  5  limestone  shingle. 
III.        cement,  7J  natural  gravel  and  sand  mixed. 
IV.        cement,  3  Neckar  sand,  6  Neckar  gravel. 

V.        cement,  3  Neckar  sand,  6  limestone  shingle. 
VI.        cement,  9  natural  gravel  and  sand  mixed. 

The  ends  of  the  specimens  were  plastered  with  a  layer  of  neat 
cement  in  order  to  facilitate  planing.  The  specimens  were  taken 
from  the  moulds  at  the  end  of  one  day,  and  were  then  covered 
with  bagging,  which  was  kept  moistened,  for  28  days.  At  the 
time  of  testing  the  age  of  the  specimens  varied  from  76  to  97 
days. 


100 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


The  deformations  were  measured  by  means  of  a  specially  de- 
signed instrument  reading  directly  to  .00013  inch,  on  a  meas- 
ured length  of  about  29  inches.  The  load  was  applied  to  the 
specimens  at  a  steady  rate,  from  o  to  the  point  desired,  in  i-J-  min- 
utes, and  the  removal  of  the  load  was  accomplished  at  the  same 
rate. 

In  all  of  Professor  Bach's  experiments  the  loads  were  added 
and  removed  until  it  was  found  that  there  was  no  change  in  the 

TABLE  I. 


Composition  in  Parts  by 
Volume 

Cement  Used  —  Brand  "B" 

Cement  Used—  Brand  "L" 

tx 

0) 

0      . 

|  M 

"tl 

TJ 

^ 

Coefficient  of 

2~* 

fe 

Coefficient  of  •§ 

1 

1 

1 

1 

CO 

JS 

1 

Elasticity 
Between  Inten- 

l«l 

CO 

.C 

C 

1 

Elasticity 
Between  In- 

C 

3  e1"^ 

g 

1> 

C 

O 

sities  of  Stress 

^k 

_0 

O 

tensities  of  0  U  «co 

M 

0 

O 

& 

* 

o 
G 

of  0  and  113 
Lbs.  in  Lbs 

«  t/; 

* 

0 

and  113  Lbs. 
in  Lbs. 

£«£ 

g 

1 

u 

& 

s" 

& 

1 

per  Sq.  In." 

13 

a 

1 

per  Sq.  In. 

P    W    & 

C  .-;     . 

u 

C? 

J 

55 

oi 

< 

M 

5.5 

< 

CO 

5«5 

2^ 

— 

5 

— 

2^ 

2.37 

4,340,000 

1370 

2Yz 

2.33 

3,410,000 

880 

2/-2 

5 

— 

— 

2^2 

2.42 

4,670,000 

1780 

iy2 

2.44 

5,160,000 

1520 

2^2 

5 

— 

— 

2*4 

2.42 

5,340,000 

1980 

3 

2.46 

4,950,000 

1580 

2]/2 

5 

— 

— 

2]/z 

2.43 

4,730,000 

1800 

3 

2.45 

4,760,000 

1615 

— 

— 

7/2 

2)4 

2.39 

4,870,000 

1  865 

2^2 

2.33 

3,820,000 

1230 

— 

— 

— 

7/2 

3 

2.42 

4,970,000 

2000 

3 

2.34 

3,450,000 

1200 

— 

— 

— 

7/2 

3 

2.40 

4,480,000 

2090 

3 

2.35 

3,480,000 

1280 

3 

— 

— 

6 

2^ 

2.39 

4,470,000 

1640 

1]/2 

2.37 

3,920,000 

1090 

3 

— 

— 

6 

2^ 

2.39 

4,200,000 

1560 

3 

2.38 

3,680,000 

1000 

3 

— 

— 

6 

3 

2.39 

4,180,000 

1700 

3 

2.38 

3,910,000 

1080 

3 

6 

— 

— 

2J!^ 

2.43 

4,910,000 

1680 

2]/2 

2.46 

4,170,000 

1240 

3 

6 

— 

— 

2]/z 

2.43 

4,640,000 

1720 

2^ 

2.43 

4,190,000 

1360 

3 

6 

— 

— 

3 

2.42 

4,470,000 

1640 

3 

2.45 

4,170,000 

1230 

— 

— 

— 

9 

2/^ 

2.42 

4,270,000 

1510 

2^2 

2.34 

3,610,000 

960 

— 

— 

— 

9 

3 

2.40 

4,530,000 

1660 

3 

2.33 

3,250,000 

908 

I 

— 

— 

— 

9 

3 

2.41 

5,170,000 

I960 

3 

2.34 

3,220,000 

915 

deformation  as  found  by  a  previous  reading.  This  required,  in 
general,  when  the  applied  load  was  less  than  570  pounds  per 
square  inch,  four  to  eight  repetitions;  but  with  higher  intensities 
of  stress  the  deformations  of  the  specimen  were  found  to  be  also 
dependent  on  the  time  which  the  load  remained  on  the  specimen ; 
that  is,  the  strain  was  a  function  of  both  the  load  and  the  length 
of  time  the  load  was  applied.  This  agrees  with  experiments 
made  on  some  other  materials,  more  notably  those  made  by  Pro- 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 

X  X  X  X 


1 0 1 


VjO     >wO     WJ      ^C 


kO     kO     -i     ~ 

^^ 


1*1       I    O    I 


.1  *al    lovl   iv*l    I   M   I 


5  2 

o  5" 


13° 


^>  vr 

^  ^ 

0  0 


0 


00      kO      VJ      00    kO  W*    GN  ^ 

CD    ^J«    VS    v«o.t».(jNkOkO 

O     O    O    00000 


tO     kO     kO     kO     kOkOkOkOkOkOkOtOtOkOtOkOkOkOkOtO— 'kOkOtO 


*-o  kO  vjo  to 


_t».  tO  *- 

O  kO  O 

O  O  O 


00 

88 


. 

580^ 


^.  ys  to  to 

tO  ^—  vj  "Jo 


So  o  8  p  8 


tOi—tOi-i          kO^kOtO          tOkO          ^kOtO>-«kOUOtO 


W  \Q  CD  O 
4x  4i-  ^5  OJ 
O  O  O  O 


^  -t*-  ^>^  ^  ^J^   kO 
i—  i  ^ji  to  vj  (7\  (T\  * 

O  O  O  O  O  O 


Number  of  Speci- 
mens Tested 


Cement 


Sand  from 
Danube 


Sand 
Egginger 


Gravel  from 
Danube 


Broken 

Limestone 

Shingle 


f 


3- 

SSL 


Ultimate  Resistance 
to  Crushing 
in  Lbs.  per  Sq.  In. 


Specific  Gravity 


0-112 
bs.  per  Sq 


r 

cr 
P 
•a  o 


o  o  o  o  o 

80  o  o  o 
o  o  o  o 


. 
-U 

0 


o  —  i  —  v^o  to  o  -&. 

CD  kO  VI  M  \Q  O  O 

o  o  o  o  o  o  o 


o  o  o 

888 


Coeffi 
fo 


t  of  Elasticity  in  Lbs.  per  Sq 
Compressive  Stress  Between 
the  Limits  of— 


102  COMPRESSIVE  PROPERTIES.  [Ch.  VI. 

fessor  Thurston.  This  question  is  of  the  greatest  interest  in  con- 
nection with  the  fatigue  of  materials.  Table  I.  shows  the  results 
obtained. 

The  second  set  of  experiments,  which  were  recorded  by  Pro- 
fessor Bach  in  the  issue  of  the  28th  of  November,  1896,  were 
made  on  two  sizes  of  round  cylindrical  specimens,  the  first  being 
39.4  inches  high,  with  a  diameter  of  9.9  inches,  and  a  consequent 
cross  section  of  77^  square  inches;  the  second  being  cylinders 
of  the  same  cross  section,  but  only  9.9  inches  high.  The  experi- 
ments on  the  elasticity  of  the  material  were  made  only  on  the 
larger  specimens,  the  deformations  being  measured  on  a  length 
of  about  29^  inches,  by  the  same  instrument  noted  before,  read- 
ing directly  to  .00013  inch.  Loads  were  applied  at  intervals 
of  112  pounds  per  square  inch.  The  average  age  of  the  speci- 
mens at  the  time  of  testing  was  about  three  months.  The  con- 
crete was  prepared  as  nearly  as  possible  in  the  same  way  as  in 
the  case  of  actual  construction  work;  water  was  added  in  such 
quantities  that  by  ramming  the  whole  mass  appeared  very  plastic. 

Table  II.  shows  in  detail  the  proportions  of  the  mixtures  em- 
ployed and  the  number  of  specimens  tested,  the  total  number 
being  102. 

The  sand  marked  "Egginger"  was  quartz  sand  with  a  little 
feldspar,  while  the  "Danube"  sand  was  river  sand.  It  will  be 
seen  that  in  almost  all  cases  the  concrete  in  which  the  stone  was 
a  limestone  attained  a  higher  ultimate  resistance  to  crushing.  It 
would  seem,  then,  that  the  gravel  concrete  should  be  the  more 
elastic ;  that  is  to  say,  it  should  yield  more  under  stress  than  the 
limestone  concrete;  the  table  shows  this  to  be  so.  Table  II.  also 
shows  clearly  the  increase  and  decrease  in  the  coefficient  of  elas- 
ticity with  the  variation  of  cement  in  the  mixtures. 

Figure  i  is  plotted  from  the  results  of  the  table  and  shows  the 
variation  in  the  coefficient  of  elasticity  with  varying  proportions 
of  cement  to  other  aggregates.  In  the  case  of  mortar,  it  will  be 
seen  that  the  coefficient  rises  from  the  neat  cement  to  a  mortar  of 
one  cement  to  one  sand,  and  then  slowly  drops  until,  with  a  mix- 
ture of  one  cement  to  three  and  one-half  sand,  it  is  about  the 
same  as  that  for  neat  cement.  The  results  as  plotted  for  the 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


103 


*>"".  4,000  0(K 


I J  3,000  00( 


limestone  and  gravel  concretes  show  a  steady  decrease  in  the  co- 
efficients as  the  ratio  between  cement  to  aggregate  increases. 
The  latter  results  in  the  case  of  the  concretes  are  perhaps  to  be 
expected,  since  it  seems  rea- 
sonable to  suppose  that  a  ma- 
terial whose  strength  depends 
on  cement  will  be  yielding  in  I* 
proportion  to  the  quantity  of  Pj 
cement  in  it.  |-~  2,000 

Professor  Bach  quotes  ex- 
periments by  Hartig,  in  "Civil 
Ingenieur,"  1893,  page  467, 
and  Baker,  in  "Civil  Inge- 
nieur," 1894,  page  718,  as  fur- 
nishing results  corroborating  the  variation  of  the  elasticity  as 
found  by  him. 

The  coincidence  in  the  rise  of  the  values  of  the  coefficient  of 


Elastic 


1:2       1:4       1:6        1.8      1:10      1:12     1:U 
Proportion  of  Cement  to  Aggregate 

FIG.  1.— BACH'S  TESTS. 


Failec 

at  1960-1 

bs. 

s 

^ 

^*~~ 

M-,^--' 

1000 

/ 

^ 

^^ 

•a!500 
laOO 

/ 

^ 

t 

/*    *. 

h    14W 

J 

z 

/ 

•o5 

f 

/  A 

S 

duo° 

,£ 

T? 

I 

^1 

/ 

ce    qoo 

I 

$V 

i  1  Cement 
Concrete]  Q  ^n<i+Gr&vel 

Age  about  3  Months 
Cylinder    9!'8  Diameter  i 
3911  High         J 
Reported  by  Bach. 
Zeitsch.  Ver.Deutsh.lng 
April  27,  1895 

o    W" 
£   800 

I 

2 

7/ 

f 

£/. 

f 

&  M 

r 

c^/ 

0   500 

i 

// 

f 

!   ^ 

200 

/ 

100 
0 

/ 

/ 

34507  89 

Decrease  in  Length  per  Inch  of  Specimen  in  .0001  Ins. 
FIG.  2. 


elasticity  as  compared  to  the  increase  in  the  specific  gravity  of 
the  material  is  worth  noting,  and  the  table  shows  clearly  that  in- 


104 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


creased  power  to  resist  distortion  accompanies  higher  specific 
gravities. 

Figure  2  is  the  only  stress-strain  diagram  inserted  illustrative 
of  Professor  Bach's  results,  because  it  is  so  thoroughly  char- 
acteristic of  all  the  results  obtained.  It  shows  completely  the 
behavior  of  the  material  almost  to  the  point  of  failure.  The 
elastic  strain  curve  differs  but  little  from  a  straight  line  for  the 
first  half  of  its  length ;  and  that  this  curve  never  shows  great  de- 
partures may  be  seen  from  the  following  average  values  of  the 
coefficient  of  elasticity  which  Professor  Bach  has  deduced  from 
the  preceding  experiments : 


Mixture  as  Given  by  Column  Headed 
"Specimen  Mark"  in  Table  II. 


I.,  V Neat  Cement 

II \:\l/2   Mortar 

III 1:3  Mortar 

IV 1 :4>£  Mortar 

VI* 1 :2^  :5  Concrete 

VIII* 1:3:6  Concrete 

XVI* ....1:5:10  Concrete 

Vllf I:2>£:5  Concrete 

IXt .1:3:6  Concrete 

XVIIt 1 :5:IO  Concrete 

*Gravel  Concrete.      tLimestone  Concrete. 


Stress-Strain  Relation,  Expressed  in 
Lbs.  per  Sq.  In.,  from  Equation 


3 


556000 


ji.ii 

5,050,000  =  — 

pi.» 
4,480,000  =  -y 

p^.n 
3,  270,000  =  ~- 

,1.14 

4,230,000  =  -y 

pi.u 

3,980,000  =  — 

£1.16 

3,  080,  000  =  -y- 

P\M 

6,500,000  =  ^- 


5,400,000  =  -  - 


5,210,000  =  —- 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE.          1 05 

As  shown,  the  value  of  the  constant  E  in  the  Bach  equation  in- 
creases over  that  calculated  in  Table  II.  in  the  same  sense  as  the 
exponent  n\  that  is,  if  n  increases,  so  does  the  value  of  E,  as 
compared  to  its  value  when  n  equals  one.  It  seems  to  the  author 
that  Bach's  refinement  is  unnecessary.  It  has  never  been  found 
necessary  to  express  the  stress-strain  relation  of  a  material  like 
steel  by  an  algebraic  expression  covering  the  entire  range  of 
stress,  and  it  will  be  shown  that  concrete  possesses  an  elastic 

TABLE  III. 
COMPRESSIVE   STRENGTH   OF   NEAT  DYCKERHOFF  CEMENT. 


Size  of  Specimen 

Crushing  Load 
in  Lbs.  per  Sq.  In. 

Average  Modulus  of 
Elasticity 
in  Lbs.  per  Sq.  In. 

I  In 
2 
3 
4 
5 
6 
7 
8 
9 
10 
II 
12 
4x 
4x 
4x 
8x 
8  x 
8x 
8x 
8x 
12  x 
12  x 
12  x 
12  x 

ch  Cu 

4x  I 
4x2 
4x3 
8x2 
8x3 
8x4 
8x5 
8x6 
12  x  2 
12  x  4 
12x6 
12x8 

be   

5896 
7094 
5937 
4847 
4610 
4283 
4987 
5007 
4754 
4761 
5374 
5291 
1  647  1 
6370 
6003 
10664 
7186 
5952 
6019 
5771 

1  Tested    in    built-up 
I      piers,  set  dry.  Re- 
f     suits  not  compara- 
1      ble. 



1,358,774 
1,421,111 
1,510,416 
1,703,877 
1,635,107 

limit,  although  not  a  precise  one,  below  which  the  stress-strain 
relation  may  be  expressed  by  a  constant. 

General  Q.  A.  Gillmore  treats  very  extensively  of  the  com- 
pressive  resistance  and  elasticity  of  Portland  and  natural  cement 
mixtures  in  his  book,  "Notes  on  the  Compressive  Resistance  of 
Free  Stone,"  etc.,  published  in  1888.  The  accuracy  of  the  tests 
appears  to  be  insured,  since  they  were  all  made  at  the  Water- 
town  Arsenal. 


106  COMPRESSIVE  PROPERTIES.  [Ch.  VI. 

In  the  case  of  the  neat  cement  experiments,  abstracted  in 
Table  III.,  a  series  of  cubes  and  prisms  was  made  of  Dyckerhott 
Portland  cement,  the  average  age  of  the  specimens  at  the  time 
of  testing  being  one  year,  ten  and  one-half  months.  The  cubes 
varied  in  sizes,  by  increments  of  one  inch,  from  one  to  twelve 
inches  on  the  side,  there  being  six  samples  of  each  size.  The  ma- 
jority of  the  specimens  which  were  tested,  including  both  the 
cubes  and  prisms,  had  plastered  faces,  the  exceptions  being  a  few 
of  the  2,  3,  4,  5,  6,  7,  8,  9,  10  and  n  inch  cubes.  It  should  be 
noted  that  plastering  the  compressed  surfaces  uniformly  increases 
the  ultimate  resistance. 

It  will  be  seen  that  in  the  case  of  the  cubes  the  smaller  cubes 
gave  slightly  higher  crushing  resistances  than  the  others ;  that  in 
the  case  of  the  prisms  the  very  flat  prisms  furnished  extremely 
high  values.  This  is  to  be  expected.  It  will  be  seen  that  the 
average  value  is  about  5,000  pounds  per  square  inch.  The  co- 
efficient of  elasticity  was  determined  for  the  larger  cubes,  and  in 
calculating  these  values  General  Gillmore  divided  the  unit  stress 
at  a  point  which  he  names  the  elastic  limit  by  the  unit  deforma- 
tion, no  deduction  being  made  for  permanent  set;  these  coeffi- 
cients, therefore,  are  not  the  true  elastic  coefficients;  they  would 
be  greater  than  given  in  the  table. 

Figure  3  shows  the  stress-strain  curve  determined  for  one  10- 
inch  cube,  and  also  for  one  1 2-inch  cube.  The  curves  are  char- 
acteristic of  all  the  tests,  although  some  show  a  slight  convexity 
to  a  horizontal  line  at  the  origin.  This  may  possibly  be  due  to 
the  squeezing  out  of  the  plaster  between  the  specimen  and  the 
bed  plate,  since  it  seems  that  the  deformations  were  measured 
between  the  heads  of  the  testing  machine.  The  majority  of  the 
curves  shown  by  General  Gillmore  are,  however,  very  similar  to 
Figure  3.  The  elastic  limit  might  be  placed  at  .6  to  .75  of  the 
ultimate  resistance. 

Table  IV.  gives  the  values  of  the  ultimate  resistance  obtained 
by  General  Gillmore  for  mortar  and  concrete  cubes  mixed  with 
three  different  brands  of  cement — two  natural  and  one  Portland. 
Each  result  shown  is  an  average  of  two  specimens,  the  beds  of 
all  specimens  being  plastered  before  being  tested.  Some  of  the 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE.          1 07 


k**       p 
™      OQ 

pi 
Tf 

•fl     fs 

I  f 

o 


Total  Load  on  Specimen  in  Pounds 

1       I        I       i       I       i       i 
I      i       i      I      I       1      1 


108 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


cubes  were,  in  addition,  placed  between  wooden  pine  cushions, 
but  it  was  invariably  found  that  the  use  of  these  wooden  cushions 
did  not  develop  the  full  possible  strength  of  the  material. 

In  the  table  as  given  no  distinction  has  been  made  between 
specimens,  whether  they  were  provided  with  such  cushions  or 
not.  The  coefficient  of  elasticity  could  only  be  determined  for 


.02  .03  .(it- 

Decrease  in  Total  Length  in  Inches 

FIG.   4.— FROM   GILLMORE'S  TESTS. 

those  specimens  in  which  no  wooden  blocks  were  used,  because 
the  deformations  were  measured  directly  between  the  heads  of 
the  testing  machine  and  the  concrete  was  forced  rather  deeply 
into  the  wooden  cushions. 

The  values  shown  have  this  peculiarity:  that  the  concretes 
seem  to  possess,  on  the  whole,  a  greater  strength  than  the  mor- 
tars, which  is  rather  exceptional,  and  can  perhaps  be  explained 
only  by  the  fact  that  the  mixtures  were  better  balanced. 

Table  V.  shows  the  values  of  the  coefficients  of  elasticity  of 
the  larger  size  cubes,  determined  in  the  same  manner  as  in  the 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


109 


Total  Compressive  Load  in  Pounds 

tO  G*  rf*  O'  CT-  ~J 

II          S         8         1         8 

§         1          I         I         1         1 


110 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


case  of  the  neat  specimens  of  Table  III.     The  intensity  of  stress 
for  which  these  coefficients  are  calculated  is  shown. 

Figures  4  and  5  are  characteristic  stress-strain  curves  of  all 
the  mortar  and  concrete  tests.  It  will  be  seen  that  there  is  a 
point  which  might  be  called  the  elastic  limit,  although  all  the 

TABLE  IV. 


Brand  of 
Cement 

Composition  of  Specimen 
Parts  by  Volume 

Size  of  Specimen  Cubes 

2 

In. 

4 
In. 

6 
In. 

8 
In. 

10 
In. 

12 
In. 

14 
In. 

16 
In. 

18 
In. 

Cement 

•g 

& 

u 

1 

B 
«  « 

11 

Ultimate  Compressive  Resistance  in  Lbs.  per  Sq.  In. 

A.. 
B." 

C." 

I  (DryMeas.) 
I  (Paste) 

3 
3 

IK 
3 

IK 
3 
3 
3 

2 

4 

6 
6 

6 

1429 

758 
1032 
2042 
1324 
2322 
1633 
3450 
4014 

800 
1  127 
1340 
750 
963 
1000 
2655 
2629 

707 

1035 
1746 
790 
1434 
861 
2469 
3025 

945 
1  167 

685 
972 
1346 
688 
1560 
765 
2434 
2690 

715 
723 

612 
856 
1247 
718 
1447 
843 
2519 
2978 

941 

A — Newark  Co.'s  Rosendale;  tested  at  age  of  about  22  months. 
B— Norton's  Natural;  tested  at  age  of  about  3  years  and  10  months. 
C— National  Portland;  tested  at  age  of  about  3  years  and  10  months. 

specimens  show  considerable  permanent  deformations  at  fairly 
low  stresses.  This  elastic  limit  might  be  taken  between  two- 
thirds  and  three-quarters  of  the  ultimate  resistance.  None  of 

TABLE  V. 


Brand  of 
Cement 

Composition  of 
Specimens 

Size  of  Specimen 

lliJ 

Cement 

•o 
w 

Stone 

Cube 

Sin. 

10  In. 

12  In. 

16  In. 

18  In. 

Q  "     J 

Coefficient  of  Elasticity  in  Lbs.  per  Sq.  In. 

Newark      ) 
Rosendale  ) 
Norton's  Nat.  . 

National  Port. 

1 

1 
1 
1 
1 

1 
1 

3 

3 

3  2 
3 
3 

(2  Gravel) 
1  4  Stone    j 

6 
6 

6 

1,092,000 
1,076,000 

549,000 

465,000 

614,000 
573,000 
708,000 
702,000 
1,606,000 
1,350,000 

572,000 

655,000 
484,000 
778,000 
530,000 
1,864,000 
1,732,000 

567,000 

650 

750 
410 
800 
500 
1800 
1500 

the  curves  show  the  coefficient  to  be  a  constant  quantity,  and  not 
much  error  is  introduced  if  it  is  taken  constant  below  the  assumed 
elastic  limit. 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


11 


Table  VI.  gives  the  results  of  Henby's  compression  tests  on 
stone  concrete  and  cinder  concrete,  these  tests  having  been  made 
at  the  same  time  and  in  the  same  manner  as  the  tension  tests 
noted  in  Art.  20. 

TABLE  VI. 
COMPRESSION  TESTS— STONE  CONCRETE. 


1) 
H 

09 

Composition- 
Parts  of 

cS 
JS-g 

»i 

Modulus 

M.5 
4> 

0  c 

of 

cm/? 

0 
u 

Q 

£ 

°c 

Treat- 
ment 

.5  £ 

Elasticity 
Lbs.  per 

VJC/J 

£  k 

C   ®~ 

Con- 
sistency 

Remarks 

a 

S 

•o 

c 

C  g 

«8 

^U 

Sq.  In. 

3 

2 

M 

u 

at 

S 

C/5 

OQU 

N    O 

Ss 

M 

220 

90 

2 

4 

A 

2 

Air  dry 

140 

4,421,000 

1243 

Dry 

221 

90 

2 

4 

4i 

2 

44 

144 

5,792,000 

982 

ii 

80 

2 

5 

44 

2 

44 

146 

3,927,000 

726 

44 

272 

60 

3 

6 

2 

Air 

2,886,000 

413 

Very  dry 

225 

30 

2 

4 

156 

44 

160 

7,171,000 

3020 

Plastic 

226 

30 

2 

4 

Water 

152^ 

4,625  000 

2610 

76 

9 

2 

5 

\% 

Air 

152 

4,930,000 

423 

44 

248 

32 

2 

5 

\yz 

44 

151 

5,055,000 

2097 

4 

249 

32 

2 

5 

\l/i 

Water 

154^ 

7,292,000 

2830 

4 

250 

34 

3 

6 

1/2 

Air 

143 

5,104,000 

1310 

4 

251 

39 

3 

6 

15£ 

44 

146 

7,520,000 

1733 

4 

252 

39 

3 

6 

14 

\YZ 

Water 

152 

6,646,000 

2242 

4 

253 

38 

4 

8 

44 

\% 

44 

143 

4,560,000 

1282 

4 

291 

90 

i 

— 

— 

M 

— 

44 

136 

6,578,000 

5280 

4 

\  Sudden 

292 

90 

i 

— 

— 

— 

Air 

129 

3,940,000 

4580 

4 

)  Failure 

254 

38 

i 

4 

8 

A 

i^ 

44 

139 

2,446,000 

617 

Excess 

255 

38 

i 

4 

8 

151 

138 

2,247,000 

797 

CINDER  CONCRETE. 


49 

50 

2 

4 

48 

152 

30 

2 

154 

tt 

189 

30 

2 

190 

138 

60 

2 

139 

tt 

140 

60 

216 

217 

60 

3 

193 

30 

218 

3/t> 

A—Atlas  Cement ;    M— Medusa  Cement. 

It  will  be  seen  that  the  ultimate  compressive  resistance  de- 
creases very  uniformly  as  the  percentage  of  materials  other  than 
cement  in  the  mixture  increases,  and,  also,  that  the  modulus  of 
elasticity  increases  with  the  ultimate  resistance.  The  compress- 
ive resistance  of  the  neat  cement  cubes  is  about  5,000  pounds  per 


112 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


square  inch  and  reduces  to  about  1,000  pounds  for  a  1:4:8  mix- 
ture. These  compressive  resistances  have  been  plotted  in  the 
usual  manner  in  Figure  6  and  the  results  averaged  by  means  of 


4800 

•S  4000 

"**.,, 

± 

$* 

No 

S  01 

Lot 

*T 

JW 

L 

^ 

9J> 

We 

rag 

eN 

0.0 

sts 

j   U, 

x 

S 

2 

X, 

s^ 

1 

'2 

< 

S^e 

C 

{tltf 

•^  C 

** 

^ 

X 

"^**^. 

<)-. 

*: 

**» 

X 

x 

1 

I 

2 

0     1 

i  i 

2     1 

3     ] 

i    1 

5     1 

6     1 

7     1 

Parts  of  other  Material  to  Cement 
FIG.  6.— FROM   HENRY'S  TESTS. 


a  straight  line,  which  may  be  expressed  algebraically  by  the  fol- 
lowing equation: 

*=4350— 2587 (i) 

For  Eq.  (i),  then,  it  will  be  seen  that  a  neat  cement  mixture 


1100 


1000 


4*900 

't 


800 


700 


400 


200 


.0001  .0004  .001 

Proportionate  Deformation 
FIG.  7.— FROM   HENRY'S  TESTS. 


.0018 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE.          1 1 3 


will  have  an  ultimate  resistance  of  4,350  pounds,  and  that  a  mor- 
tar of  i  cement  to  i6J  parts  of  other  materials  will  have  no 
strength  at  all. 

Table  VI.  also  furnishes  results  of  ultimate  compressive  re- 
sistances and  coefficients  of  elasticity  for  the  cinder  specimens, 
and  the  results  of  these  tests  are  also  plotted  in  Figure  6;  but  it 
has  not  been  thought  proper  to  express  these  results  by  means 
of  an  equation. 

Figure  7  shows  some  stress-strain  curves  of  compression  tests 
made  on  the  cinder  concrete.  In  this  case  the  elastic  limit  might 
be  considered  to  be  one-half  of  the  ultimate  resistance. 

From  an  examination  of  the  coefficients  of  elasticity  deter- 
mined by  Henby  it  is  impossible  to  check  Bach's  proposition 
that  there  is  some  mixture  which  attains  the  highest  value  of 
the  coefficient,  and  that  mixtures  either  leaner  or  richer  have  de- 

TABLE  VII. 


Brand  of  Cement 

Mixture 

Average  Com- 
pressive  Strength, 
Lbs.  per  Sq.  In. 

Coefficient  of  Elasticity  in  Lbs. 
per  Sq.  In.  Between  Loads  of 
100  and  600  Lbs.  per  Sq.  In. 

•  I  '3 

2001 

•2*3 

16^4 

,, 

,, 

•2-4 

TQoe; 

,, 

,, 

:2:5 

1084 

" 

- 

:3:6 

788 



Alpha    Portland.... 

:I:3 

2834 

2,500,000 

" 

" 

:2:5 

1600 

1,279,000 

Atlas 

" 

:I:3 

2414 

3,125,000 

" 

"         

:2:5 

1223 

1,138,000 

creasing  values.  In  these  experiments  the  value  of  the  coeffi- 
cient decreases  rather  uniformly  as  the  mixtures  become  more 
lean. 

Table  VII.  is  taken  from  the  Watertown  Arsenal  Report  for 
1898,  and  shows  results  of  tests  made  on  cinder  concretes  for  the 
Eastern  Expanded  Metal  Company  of  Boston.  In  all  84  twelve- 
inch  cubes  of  various  ages,  made  with  different  brands  of  ce- 
ment, were  tested.  Only  the  results  of  the  better  known  brands 
are  here  abstracted,  and  only  those  which  reached  the  age  of 
about  three  months.  Each  result  shown  is  an  average  of  three 
tests.  The  cinder  used  was  in  the  condition  in  which  it  came 


114 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


from  the  furnace;  it  was  not  sifted,  and  only  the  larger  clinkers 
were  broken. 

In  the  same  Watertown  Arsenal  Report  for  1898  are  also  re- 
corded results  of  tests  on  95  cubes  and  prisms  which  were  manu- 
factured at  the  Arsenal.  Only  those  specimens  in  which  Alpha 
cement  was  used  are  shown  in  Table  VIII.,  the  mixtures  being 
1:1:3.  The  sand  was  bank  sand,  the  pebbles  were  from  the  Ar- 

TABLE  VIII.— 12-INCH  CUBES— 1:1:3  ALPHA  CEMENT. 


Kind  of  Stone 

Ultimate  Compressive 
Resistance  in  Lbs.  per 
Sq.  In.  at  Age  of  — 

Coefficient  of  Elasticity  in 
Lbs.  per  Sq.  In.  Bet   Loads  of 
100  and  600  Lbs.  per  Sq.  In. 
at  Age  of— 

About 
1  Month 

About 
2  Months 

About 
1  Month 

About 
2  Months 

Trap  Yz  Inch 

2800 
3200 
4917 

4349 

4800 

2992 
5024 
3817 
3800 

3000 
4140 
2700 

2190 
3800 
3572 
4400 
5551* 

5021 

3,571,000 
8,333,000 
6,250,000 

8,333,000 

8,333,000 

4,167,000 
6,250,000 
4,167,000 
4,167,000 

3,125,000 

5,000,000 

4,167,000 

3,125,000 
4,062,000 
5,208,000 
5,000,000 
5,000,000 

4,167,000 

8,333,000 
6,250,000 

8,333,000 

3,125,000 
12,500,000 
2,778,000 
5,000,000 

3,125,000 
12,500,000 

"       3/       " 

14         T                       H 

5272 
4544 

5542* 

3870 
4700 
4018 
3490 

3800 
4523 

/Trap  y2  Inch  I   Part    \ 
\     "  V/2     "     --I  Parts] 
f     "   2>£     "     ....  I   Part  -^ 

{  ::  '*  :  ::::!  :  } 

Pebbles  Y%  Inch 

f  Trap  2^  Inch  2  Parts  \ 
\  Gravel  l/&  Inch.  .  .  I  Part  J 
Pebbles  \Yt   Inch  

f  Pebbles    #  "    .  .  I   Part    \ 
\        "        \Y2   "    ..2  Parts/ 
f  Gravel  l/&  Inch....  I  Part) 

\      "    X    "  ...-I    "   \ 

\  Pebbles  \%  Inch..  I     "    J 
Trap  iy2  Inch  
(  Trap  1V2  Inch  I    Part) 
{  Pebbles  #  Inch...  I      "     V 
1  Gravel  %  Inch.  .  .  .  I      "    J 
Mixture  1:3:6  of  I  In.  Trap.  . 
Pc>hKlc><;  I  l/>  In     to  1  In 

Trap  I  ^  Inch 

I  '  I   Mortar  

4800 

6,250,000 

*Not  fractured. 

senal  grounds  and  the  rock  was  broken  trap  of  different  sizes 
from  Waltham,  Mass.  The  f  inch  stone  all  passed  a  f  inch  sieve 
and  was  all  retained  on  the  next  smaller  size,  viz.,  J  inch.  The 
other  graded  sizes  were  obtained  in  a  similar  manner.  The  ages 
of  the  specimens  varied  from  7  to  76  days;  only  those  having  an 


Art.  2 1 .  ]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


115 


age  of  30  to  70  days  need  be  discussed,  since  the  others  are  of  no 
practical  importance.     As  shown,  the  results  are  for  one  speci- 

TABLE  IX. 


Brand  of  Cement 

Approx  mate  Composition 
by  Parts 

Modulus  of  Elasticity  in  Lbs. 
per  Sq.  In.  Between  Loads 
per  Sq.  In.  of 

•SjJd 

3.2J«5 

08  a* 
.«„<» 

•Z  Mo  u 

5.sg£ 

Cement 

Sand 

Stone 

100-600 

100-1000 

Gcncsce  

I 
I 

I 

I 

2 
3 
4 
*) 
6 

2 
3 

4 

2 
3 
4 
5 
I 
2 
3 
4 
5 
2 
3 
4 
2 
3 
4 
2 
3 
4 
2 
3 
4 

2 
3 
I 
2 
3 

5 
7 
9 
12 
15 
16 
4 
6 
8 
II 
5 
7 
9^ 
12^ 
15 
4K 
6^ 
8 
II 
12 

7K 
10 

15 
6*/2 
8^ 
II 
7 
10 
13 
6^ 
8 
10/2 
5 
7 
9 
4 
5^ 
8 

2,428,000 
2,619,000 
2,108,000 
1,403,000 
1,370,000 
1,087,000 
1,628,000 
2,263,000 
1,745,000 
1,801,000 
1,822,000 
2,314,000 
2,018,000 
1,528,000 
1,427,000 
3,072,000 
2,285,000 
1,845,000 
1,449,000 
1,318,000 
2,518,000 
1,752,000 
1,408,000 
3,273,000 
2,168,000 
1,792,000 
2,874,000 
2,292,000 
1,608,000 
2,685,000 
2,609,000 
2,081,000 
2,781,000 
2,609,000 
1,528,000 
2,780,000 
2,516,000 
1,602,000 

2,113,000 
2,748,000 
1,974,000 
1,382,000 
1,300,000 

4080 
3291 
2930 
2226 
1842 
1365 
3330 
2519 
2567 
2094 
4165 
3221 
2311 
1851 
1713 
4031 
3465 
2230 
1843 
1723 
2852 
1927 
1665 
3678 
2296 
1880 
3521 
2460 
1774 
3579 
2545 
1899 
2928 
2459 
1495 
3127 
2377 
1393 

,, 

,, 

,, 

ti 

44 

1,508,000 
2,081,000 
1,580,000 
1,499,000 
1,749,000 
2,002,000 
1,721,000 
1,432,000 
1,273,000 
2,265,000 
1,991,000 
1,555,000 
1,218,000 
1,100,000 
2,295,000 
1,227,000 

tt 

.t 

,, 

Wayland 

,, 

tl 

tl 

,, 

" 

tt 



2,937,000 
1,757,000 
1,468,000 
2,505,000 
1,890,000 
1,266,000 
2,446,000 
2,176,000 
1,622,000 
2,253,000 
2,207,000 
1,046,000 
2,571,000 
2,228,000 

lt 

Empire  

.. 

4, 

44 

lt 

Champion  

tt 

,< 

44 

44 

men  only.  It  will  be  seen  that  the  values  of  the  coefficient  of 
elasticity  are  very  high.  This  may  be  explained  by  the  density 
of  the  specimens,  which  averaged  about  150  pounds  per  cubic 


116 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


foot;  whereas,  in  the  tests  made  by  Rafter,  and  to  be  noted  later, 
the  average  weight  was  only  about  140  pounds  per  cubic  foot. 

Table  IX.  is  taken 
from  the  Watertown 
Arsenal  Report  for 
1898  and  records  ex- 
periments made  for 
Mr.  George  W.  Rafter 
on  twelve-inch  cubes 
of  concrete  made  with 
various  brands  of  ce- 
ment. Mr.  Rafter's 
tests  are  explained  in 
greater  detail  on 
page  121  et  seq. ;  here 
are  only  given  the  experiments  concerning  the  elasticity.  The 
average  age  of  the  specimens  was  about  one  year,  seven  and 

one-half  months. 
The  majority  of 
results  are  aver- 


.001 .006  .01  .015 

Deformations  in  Gauged  Length  in  Inches. 
FIG.  8. 


.017 


.005  .01  .015 

Deformations  in  Gauged  Length  in  Inches. 
FIG.  9. 


ages  of  tests 
made  on  two  to 
four  specimens ; 
n  o  distinction 
has  been  drawn  between  dry,  plastic  or  excess.  The  gauged 
length  on  which  the  elastic  properties  were  measured  was  five 
inches.  The  experi- 
ments are  tabulated  in  •- 

* 


the  order  of  the  richness 
of  the  various  mixtures. 
It  will  be  seen,  in 
general,  that  the  values 
of  the  modulus  of  elas- 
ticity decrease  with  the 
leanness  of  the  mixture. 
The  ultimate  crushing 
resistance  also  decreases 


.001  ,001  .007  .01  .015 

Deformations  in  Gauged  Lengthjn.lnches. 

FIG.  10, 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE. 


17 


3000 


Composition: 

Wayland  Cement  1     ) 

_J    Saud  1      t 

Broken  Stone        6.43/ 

Consistency  of  Mortar,  Plastic 

Age,  1  Year,  3  Mos..  20  Days 


Ironclad  Cement  1    "\ 
Sand  1     [ 

Broken  Stone       7.76) | 

Age,  1  Year.  7  Mos.,  15  Days 


Wayland  Cement  1    \ 

3 

Broken  Stone       8.29'- 


Age,  1  Year,  8  Mos.,  17  Days 


Empire  Cement  1 
Sand  2 

Broken  Stone     7.5 
Age.  1  Year,  8  Mos.,  It  Days 


Mortar 

Empire  Cement  I  \ 

Sand  4) 

Age,  1  Year,  7' Mos.,  22  Days 


Mortar 

Empire  Cement  1} 

Sand  2J 


Age,  1  Year,  7'  Mos.,  18  Days 


Mortar 

Empire  dementi 


Age,  1  Year,  7  Mos.,  18  Days 


Mortar  Prism 

6"x6"xl8"    - 

Alpha  Cement  1  > 

Fine  Sand          1 ) 

Age.  as  Days 


Mortar  Prism 

6"x6"xl8" 

Age,  38  Days 

1  Day  in  Mold  ) 

37  Day  s  in.  Water) 

Gaugeu  Jjcnfrth  10 


35  Days  in  Wate 
Gauged  Length  10 


.03        .04  .01        .02       .03        .04 

Deformations  in  Gauged  Length  of  5  Inches. 


FIG.  11. 


.03 


118 


COMPRESS1VE  PROPERTIES. 


[Ch.  VI. 


with  the  leanness  of  the  mixture;  in  other  word's,  the  modulus  of 
elasticity  is  some  function  of  the  ultimate  crushing  resistance. 

Table  IX.  also  shows  that  the  modulus  is  not  a  constant  quan- 
tity for  any  one  specimen.  The  values  given  are  calculated  be- 
tween two  increments  of  stress,  from  100  to  600  pounds  and  from 
100  to  1,000  pounds  per  square  inch.  In  every  instance  the  val- 
ues for  the  second  increment  of  stress  are  smaller. 

Figures  8  to  12  are  all  abstracted  from  the  Watertown  Ar- 
senal Report  for  1898  and  1901,  and  show  clearly  the  elastic  be- 
havior of  some  of  the  mixtures  which  have  been  tabulated  on  the 


Specimen  same  as  below 
Age,l  Year,  6  Mos.,  K  Das 


Set  in  Mold,  23  Hours  ) 

Cool  Cellar;    1  Year,  5  Mos.,  28  Das. f 
la  Air.  27  Das.  ) 


1      Genesee  Cemen 

1       Sand 

4. 71  Broken.  Stone 


Set  in  Mold,  ,23  hours 

17  Das. 
10  Das. 


Consistency  of  Mortar,  Dry 
ige,  1  Year,  9  Months,  5  Days 
Wt.  per  Cu.Ft.  =  147.16  Ibs 
Specimen  12"  Cube 
Gauge  Length  =-5  Ins. 


.001 


.01  .015 

Deformation  in  Gauged  Length  in  Inches 

FIG.  12. 


preceding  pages.  Two  curves  are  shown,  the  one  to  the  right 
being  the  curve  of  total  deformation  and  the  other  the  curve  of 
sets.  The  curves  are  characteristic  of  all  the  tests  made,  and  in- 
spection tends  to  confirm  the  opinion  that  concrete  mixtures  in 
compression  have  a  point  which  might  be  called  the  elastic  limit, 
at  about  5-10  or  6-10  of  the  ultimate  crushing  resistance.  In  the 
case  of  the  neat  cements  or  mortars,  this  elastic  limit  approaches 
more  closely  to  the  ultimate  resistance,  having  a  value  of  perhaps 
8- 1  oof  it. 

Professor  E.  J.   McCaustland  records  in  the  Transactions  of 


Art.  21.]     COEFFICIENT  OF  ELASTICITY  AND  RESISTANCE.          1 1 9 


the  American  Society  of  Civil  Engineers,  1903,  some  experi- 
ments which  he  made  on  concrete  and  mortar  columns  of  various 
compositions  and  of  various  ages,  and  for  which  he  determined 
the  true  coefficient  of  elasticity  at  500  pounds  per  square  inch. 

Table  X.  shows  the  results  of  his  tests  on  these  columns,  which 
were  circular,  10  inches  in  diameter  and  40  inches  long.  It  will 
be  seen  that  the  coefficients  varied,  although  not  uniformly,  with 
the  variation  in  the  ultimate  compressive  resistance,  and,  from 
the  stress-strain  curves  which  are  shown  in  the  original  paper,  the 
material  might  be  said  to  have  an  elastic  limit  of  5-10  to  6-10  of 
the  ultimate  resistance. 

TABLE   X. 


Proportions 

Age  in 
Months 

Coefficient  of 
Elasticity  in 
Lbs.  per  Sq.  In. 

Ultimate  Crushing 
Strength 
Lbs.  per  Sq.  In. 

Cement 

Sand 

Broken  Stone 

2 

3 

14 

,050,000 

1000  N 

2 
2 

3 
3 

II 

13 

,530,000 
,060,000 

1752 
1215 

1654 

2 

3 

14 

,010,000 

2650 

3 

4 

10 

,100,000 

1484 

3 
3 

4 
4 

II 
14 

,380,000 
,425,000 

1382 
1230 

141  1 

3 

4 

II 

,441,000 

1550 

3 

5 

14 

,450,000 

1550 

3 
3 

5 
5 

14 
14 

,531,000 

1500 
1792 

•  1504 

3 

5 

14 

,050,000 

1  170 

2 

5 

15 

840,000 

10451 

2 
2 

5 
5 

15 
14 

,510,000 

,372,500 

1955   i  1532 
1450  f  l 

2 

5 

23 



1680  J 

4 

— 

23 

2,775,000 

2660 

I 

2 

— 

23 

4,625,000 

3410 

I 

3 

— 

23 

3,700,000 

2250 

Figure  13  presents  the  results  of  compressive  experiments  re- 
ported by  Professor  Edgar  Marburg  to  the  American  Society 
for  Testing  Materials,  at  its  annual  meeting,  1904.  These  stress- 
strain  diagrams  represent  tests  on  four  6x6-inch  prisms,  24  inches 
long;  the  deformations  were  measured  on  a  gauge  length  of  18.5 
inches.  The  concrete  was  composed  of  i  part  of  Delaware  River 
bar  sand,  to  2  parts  of  Atlas  Portland  Cement,  to  4  parts  of  J-inch 
broken  trap  rock ;  the  materials  were  mixed  rather  wet.  The  age 


120 


COMPRESSiVE  PROPERTIES. 


[Ch.  VI. 


of  the  specimens,  all  being  stored  in  air,  was  30  days,  and  the 
average  weight  154  pounds  per  cubic  foot. 


::: 

-    1 

^-^i^^^-^^ 

1   j 

EHEE 

Lr 

___-,  __j_|_,-. 

7^~~          T]3  "r5~ 

- 

' 

„.       .     ..'",.!,    ,,r 

~~*-fi~       Til' 

--; 

» 

Jr 

« 

xT^ 

BffrFFrW     :: 

1 

::£» 

+f-^-+y-+rr— 

j  —  p 

; 

IT 

q 

i 

y 

a.       i    / 

L 

5 

z: 

1  l  '  vf  i  i  1  1-^-  1  [  y  - 

Material,  1  :i! 

:4  Concrete.  Age  30  daya 
s  GLength  34" 
measured  between 
ved  to  Specimen 
18" 

Specimens  6 

i 

i/*             f  • 

J 

. 

T~_ 

'        f  . 

,,i 

~  -^  " 

-T- 

r>H  —  H~i~i  —  4  '  — 

r 

H: 

i 

7'    1                            i  »  1 

-Jf 

_!_ 

f  : 

j 

i 

4- 

'—  --  —  !  —  !-r-  -i-  —  r*- 

(Eh 

-  •:•! 

* 

-*-.  —  r-  1  —  H  —  r"n~i  —  r 

|||'  1  

| 

•  — 

i 

1 

J-  -L        -a- 

I   | 

si 

.           . 

•4- 

1 

:E 

]         ! 

i 

^G: 

i 

i 

n~i    i    !  •-     -  "i 

~  '  i 

i 

nc 

i 


i 


O^'OOOO  O."0005  O."0010    O."0000  O."0005 

Ol'OO  O."0005  O."0000 

Compression  per  inch  length 


0.0005 


FIG.  13.— MARBURG'S   TESTS. 

The  figure  shows  the  stress-strain  curve  to  be  sensibly  a 
straight  line  to  a  point  about  one-half  the  ultimate  resistance. 

The  values  of  the  compressive  coefficient  of  elasticity,  calcu- 
lated without  reference  to  any  permanent  set  occurring  in  con- 
nection with  the  applied  stresses,  are  given  in  the  following  table; 
the  specimens  in  the  figure  are  numbered  from  left  to  right : 

TABLE  XI. 


Specimen 
No. 

Ultimate  Compressive 
Resistance 
in  Lbs.  per  Sq.  In. 

Coefficient  of 
Elasticity 
in  Lbs.  per  Sq.  In. 

Determined  for 
Stresses  of— 

1 

1  166 

2  000  000 

0      'SOO  I  h<;    rtpr  Sn     In 

2             .... 

1154 

2  000  000 

0  —  500            "                " 

3  
4    

1277 
1316 

2,300,000 
2,700,000 

0—500 

0  —  600 

It  is  seen  that  the  coefficient  increases  with  the  ultimate  re- 
sistance. 

Professor  Marburg  also  furnishes  the  average  ultimate  com- 
pressive resistance  of  nineteen  6-inch  cubes  of  the  same  materials 
and  same  age,  but  taken  from  batches  mixed  at  various  times. 
The  value  given  is  1643  pounds  per  square  inch.  Two  specimens, 


Enlarged  Views  of  Figures  Opposite  Page  86. 
The  Location  of  the  Points  of  Fracture,  as  Well  as  Details  of  the  Extensometer,  Are  Clearly  Shown. 


Art.  22.]  ULTIMATE  COMPRESSIVE  RESISTANCE.  1 2  \ 

mixed  with  less  water  and  thoroughly  rammed,  developed  resist- 
ances, however,  greater  than  the  ioo,ooo-pound  capacity  of  the 
machine  used. 

Art.  22.  -  Ultimate  Compressive  Resistance. 

George  W.  Rafter  has  recorded  in  the  Report  of  the  State 
Engineer  of  New  York  for  1897  results  of  compression  tests 
made  on  544  twelve-inch  cubes  whose  age  at  the  time  of  testing 
averaged  about  600  days.  The  concrete  was  prepared  in  three 
different  ways — in  dry  blocks,  in  which  the  mortar  was  only  a 
little  more  moist  than  damp  earth;  in  plastic  blocks,  in  which 
the  mortar  was  like  that  used  by  masons;  and  im  blocks,  in  which 
the  water  was  in  excess,  so  that  the  concrete  quaked  like  liver 
under  moderate  ramming.  From  every  batch  mixed  in  one  of 
these  ways  four  specimens  were  prepared  and  stored  differently. 
One  block  was  placed  in  water  from  the  time  of  making  (sum- 
mer of  1896)  until  December  i,  1896,  then  buried  in  sand  until 
January  10,  1898,  when  it  was  shipped  from  the  place  of  manu- 
facture to  the  Watertown  Arsenal  in  Massachusetts.  The  sec- 
ond block  stood  in  a  cool  cellar  until  shipment;  the  third  block 
was  exposed  to  the  weather,  and  the  fourth  block  was  covered 
with  burlap  and  was  wet  with  water  several  times  a  day  until 
November  i,  1896,  after  which  it  took  the  weather  as  it  came 
until  the  day  of  shipment.  The  tests  were  made  with  Portland 
cement  only.  The  sand  was  hand-broken  Portage  sandstone 
passing  through  a  two-inch  ring. 

Examination  of  these  detailed  experiments  shows  that  the  four 
specimens  of  any  one  series  treated  to  the  various  conditions  of 
weather  gave  rather  uniform  results;  at  least,  it  cannot  be  no- 
ticed that  any  one  condition  shows  radically  worse  effects  than 
any  other.  In  further  considering  these  experiments,  therefore, 
the  average  of  the  four  specimens  prepared  at  any  one  time  will 
be  used. 

Mr.  Rafter  does  not  express  the  ingredients  of  a  concrete  mix- 
ture in  the  usual  way,  such  as  one  part  of  cement  to  three  of 
sand,  to  three  of  stone,  either  by  weight  or  measure;  but  he  ex- 
presses the  relations,  in  percentages,  between  a  definite  mortar, 


122 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


say,  1 13,  to  a  unit  weight  of  stone.  In  order  to  make  his  results 
comparable  to  others  the  following  table  has  been  prepared, 
which  expresses  roughly  Mr.  Rafter's  nomenclature  in  the  more 


Percentage  of  Mortar 

Ratio  of  Cement  to  Sand  in  the  Mortar 

1:1 

1:2 

1:3 

1:4 

1:5 

1:6 

33  

1:1:3 

1:1:4 

1:2:7 
1:2:6 

1:3:9/2 
1:3:8 

1:4:12 
1:4:10^ 

1:5:15 
1:5:12 

1:6:16^ 

40  

usual  terms.  Two  percentages  of  mortar  to  stone  were  used,  33 
per  cent,  and  40  per  cent.,  and  six  different  mortars,  varying 
from  i :  I  to  1 :6. 

TABLE  I. 


Consistency  of  Mortar 

Parts  of 

Cement  to  Sand 

Percentage  of 
Mortar  to  Stone 

Ultimate  Crushing  Strength 
in  Lbs.  per  Sq.  In. 
Average  of  4  Specimens 

Excess  of  Water.  .  .  . 
Drv 

] 
] 
] 
] 
] 
1 
1 

4 

] 

:2 
:3 

:4 
:5 
:I 
:2 
:3 
:4 
:5 
:I 
:2 
:3 
:4 
:3 
:I 
:2 
:3 
:4 
:5 
:I 
:2 
:3 
:4 
:5 
:I 
:2 
:3 
:4 
:5 

3? 

4 

% 
% 

3764 
2847 
1723 
1767 
1441 
4267 
2888 
2056 
1810 
1537 
4072 
2777 
2207 
1600 
1586 
3256 
3168 
2016 
1670 
1400 
3966 
3404 
2179 
1671 
1559 
4123 
2960 
2027 
1750 
1465 

,, 

,, 

,, 

Plastic 

,, 

tl 

,, 

Excess  of  Water  

41                                     it 
44                                     44 

Drv.  . 

„ 

tl 

,, 

Plastic                .      .    . 

tt 

4, 

.4 

It  will  be  seen,  for  instance,  that  the  concrete  known  as  I  .-3 
niortar,  40  per  cent,  may  be  expressed  as  a  1:3:8  concrete. 


Art.  22.] 


ULTIMATE  COMPRESSIVE  RESISTANCE. 


123 


Table  I.  is  characteristic  and  shows  the  results  obtained  for 
Wayland  Portland  cements  only,  being  the  tests  numbered  29 
to  58  in  the  Report.  The  results  obtained  from  the  other  brands 
of  cements  will  be  discussed,  but  need  not  be  given  here  in  de- 
tail, since  they  show  but  little  variation. 

In  the  Transactions  of  the  American  Society  of  Civil  Engi- 
neers, December,  1899,  Professor  I.  O.  Baker  has  tabulated  and 
arranged  very  concisely  all  of  Mr.  Rafter's  experiments,  and  the 
following  tables  are  taken  from  his  discussion  of  the  experiments : 

TABLE  II. 


Plasticity  of  Mortar 

Amount  of  Mortar 

Strength  of  the  40% 
Concrete  in  Terms  of  That 
of  the  33% 

33% 

40% 

Crushing  Strength  in  Lbs.  per  Sq.  In. 

Drv    .                        

2408 
2259 
2133 

2532 
2329 
2227 

105  % 

103% 
104% 

Plastic                .  .  .  

Mean    

2267 

2363 

104% 

It  will  be  seen,  therefore,  that  the  effect  of  plasticity  is  not  of 
great  importance;  in  practice,  what  little  gain  in  strength  the 
dry  mixed  specimens  may  show  is  negligible  in  the  face  of  other 
considerations,  the  principal  one  being  the  increased  cost  of 


TABLE  III. 


Proportions  in  the  Mortar 

Amount  of  Mortar 

Strength  of  the  40% 
Concrete  in  Terms  of  That 
of  the  33% 

33%            |              40% 

Crushing  Strength  in  Lbs.  per  Sq.  In. 

I  Cement'  2  Sand  

2640 
1893 
1684 

2820 
1905 
1689 

107% 
102% 
100% 

I  Cement'.  3  Sand  
I  Cement"  4  Sand  

manufacture  of  dry  over  the  wet  concretes.     This  is  due  to  the 
extra  cost  of  the  ramming  required. 

Table  III.  shows  that  there  is  but  very  little  increase  in  strength 
of  the  40  per  cent,  concretes  as  compared  to  the  33  per  cent. 
This  may  possibly  be  explained  by  the  fact  that  in  the  33  per  cent, 
specimens  the  mortar  did  not  entirely  fill  the  voids  in  the  stone; 
the  stones  therefore  had  direct  bearing  on  each  other,  while  in  the 


124 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


40  per  cent,  concrete  the  voids  were  just  about  rilled;  the  strength 
of  the  mortar  itself  in  that  case  had  less  influence  than  the  direct 
bearing  of  the  stones  on  each  other  in  the  first  instance. 

Mr.  Rafter's  method  of  determining  the  proportions  of  the  in- 
gredients in  the  mixture  is  open  to  criticism.  The  densest  con- 
crete is  formed  when  the  sand  grains  fill  as  many  voids  as  pos- 
sible in  the  stone,  and  the  cement  grains  then  fill  as  many  as 
possible  of  the  remaining  voids  in  the  stone-sand  mixture.  This 
is  different  from  first  filling  the  voids  in  the  sand  with  cement 
and  then  the  voids  in  the  stone  with  mortar.  In  the  latter  case 

TABLE   IV. 


Brand  of  Cement 

Cement  to  Sand 
by  Measure 

Percentage  of 
Mixed  Mortar  to 
Broken  Stone 

Ultimate  Crushing 
Strength  in 
Lbs.  per  Sq.  In. 

Waj 
Say 

rland  Portland  

:2 

:3 
:4 
:6 

:2 
:I 
:2 
:3 
:4 
:5 
:6 
:2 

33^ 
42  % 

41% 
41% 
W% 

41% 
41% 

41% 

41% 
41% 
41% 

3154 

2454 
1720 
1363 
143  1 
4381 
2409 
2978 
1890 
1542 
1132 
1087 
729 
2550 

or's  Natural  

the  voids  in  the  sand  will  usually  be  found  to  be  greater  than  the 
sum  of  the  voids  in  the  stone-sand  mixture. 

Table  IV.  is  taken  from  the  Report  of  the  State  Engineer  of 
New  York  for  1894,  and  records  experiments  which  were  made 
by  Mr.  George  W.  Rafter  previous  to  those  just  tabulated.  These 
tests  were  made  on  174  concrete  cubes  of  one  cubic  foot  each 
whose  average  age  was  three  months.  The  stone  which  was 
used  was  hard  quarry  stone,  broken  to  pass  a  two-inch  ring  and 
was  washed  clean.  Each  result  shown  is  an  average  obtained 
from  two  to  six  specimens.  Some  of  the  blocks  were  placed  in 
water  after  the  final  set  had  taken  place.  The  result  obtained 
from  such  blocks  was  averaged  in  with  others  in  the  table,  it 
being  found  almost  uniformly,  however,  that  the  ones  which 


Art.  22.] 


ULTIMATE  COMPRESSIVE  RESISTANCE. 


125 


hardened  in  water,  as  compared  to  those  which  set  in  air,  were 
very  slightly  stronger.  In  these  experiments  Mr.  Rafter  also 
expressed  the  ratios  between  the  materials  by  a  relation  between 
the  broken  stone  and  the  mixed  mortar,  having  in  mind  that  the 
mortar  should  more  than  fill  the  voids  in  the  stone;  this  explains 
column  three  of  the  table. 

Table  V.  is  taken  from  the  Watertown  Arsenal   Report  for 

TABLE  V. 


Composition 

Ult.  Strength  in  Lbs.  per  Sq.  In.  at  the  Age  of 

Cement 

Sand 

Gravel 

Stone 

30  Days 

7  Months 

1  Year 

I 

IX 



4 

1448 

2213 

2917 

I 

3 

— 

?1A 

1024 

1987 

2076 

I 

2 

3 

4 

1096 

2180 

2094 

I 

2 

7 

— 

746 

1633 

1792 

I 

2^ 

8 

— 

739 

1540 

1448 

1901,  and  shows  the  ultimate  compressive  resistance,  at  various 
ages,  of  12-inch  concrete  cubes  made  from  one  brand  of  cement. 
Each  result  shown  is  an  average  of  three  tests.  It  will  be  seen 
that  this  concrete  did  not  gain  in  strength  after  seven  months. 

Tables  VI.  and  VII.  are  taken  from  the  same  Report;  the  for- 
mer shows  the  ultimate  crushing  strength  of  concrete  prisms 

TABLE   VI. 


Composition 

Number 
of 

Ultimate  Crushing 

Specimens 
Tested 

Strength 
in  Lbs.  per  Sq.  In. 

Cement 

Sand 

Stone 

I 

2^ 

/4—  l/2  In.  to  2  In.  Diam.  1 
1  Pebbles  / 

8 

2326 

I 

1l/z 

f  4—  %  In.  to  iyz  In.  Diam.  "1 
1  Gravel  J 

6 

3363 

I 

V/2 

f  4—1  In.  to  2^  In.  Diam.  \ 
\  Hard  Trap  Rock  J 

6 

3886 

6x6x36  inches  in  length,  pressed  on  their  ends,  the  average  age 
being  about  33  days.  The  results  show  that  the  same  ratio  of 
cement  to  aggregate,  but  with  different  sizes  of  stone,  may  fur- 
nish entirely  different  balancing  of  the  mixture,  and  may  thus 
affect  directly  the  ultimate  crushing  strength. 

Table  VII.  shows  the  ultimate  crushing  resistance  of  2-inch 


126 


COMPRESS1VE  PROPERTIES. 


[Ch.  VI. 


cubes  made  of  various  brands  of  neat  cement  tested  at  various 
ages.  Each  value  is  a  mean  of  from  five  to  six  specimens,  all  of 
which  set  and  hardened  in  the  air. 

The  following  series  of  compression  tests   (Table  VIII.)   on 
cement  and  mortar  bricks,  9  inches  x  4^  inches  x  3  inches,  is  re- 

TABLE  VII. 


Age 
in 
Days 

Ultimate  Compressive  Strength  in  Lbs.  per  Sq.  In. 

Storm  King 
Portland 

Alsen 
Portland 

Lehigh 
Portland 

Hoffman 
Rosendale 

Norton 
Rosendale 

Potomac 
Rosendale 

7  

I4-... 
30.... 

577 
1400 
1820 
2160 

1140 
3980 
3830 
4170 

4540 
5210 
5760 

261 
543 
676 
1010 

225 
476 
609 
878 

145 

403 

590 

1010 

corded  by  John  Grant  in  the  Proceedings  of  the  Institution  of 
Civil  Engineers,  Vol.  XXXII. ,  page  288.  Ten  specimens  were 
prepared  from  each  mixture,  the  composition  being  as  shown  in 
the  table;  five  were  allowed  to  harden  in  air  and  five  in  water, 
the  age  when  tested  being  one  year.  The  results  as  published 
are  expressed  in  tons,  and  in  reducing  the  figures  it  was  assumed 

TABLE  VIII. 


Crushing  Resistance  in  Lbs.  per  Sq.  In. 


Left 

in  — 

Cement  :  Sand 

Air 

Water 

Neat  

5370 

7350 

!•!  

4580 

4620 

I«2  .... 

3880 

3170 

1-3 

2980 

1470 

1.4 

2420 

1  160 

!•*» 

2070 

835 

1-6  

1680 

622 

1  .7  .... 

1600 

584 

j.g  

1070 

453 

I.Q.  . 

970 

412 

T.fO 

855 

312 

that  the  ton  of  2,240  pounds  was  meant.  The  specimens  were 
either  rammed  or  pressed  by  hydraulic  press  at  the  time  of 
making. 

Grant  also  made  a  series  of  tests  (Table  IX.)  on  concrete 
blocks,  some  of  which  set  in  air  and  were  so  kept  for  one  year, 


Art.  22.] 


ULTIMATE  COMPRESSIVE  RESISTANCE. 


127 


and  some  of  which  set  and  were  kept  in  water  for  the  same  period 
of  time.     The  blocks  were  either  12  or  6  inch  cubes,  but  only 

TABLE   IX. 


Proportions  of 
Cement  to  Sand 

12-Inch  Cubes 

6-Inch  Cubes 

Crushing  Resistance  in  Lbs.  per  Sq.  In. 

Kept  in  Air 

Kept  in  Water 

Kept  in  Air 

Kept  in  Water 

•  i 

2660 
2490 
1800 
1690 
1550 
1420 
1250 
1  180 
1060 
745 

2360 
2680 
1870 
1870 
1520 
1270 
1030 
840 
750 
625 

2080 
2150 
2210 
1740 
2210 
1220 
990 
840 
680 
625 

•2       

2320 
1760 
1600 
1380 
1250 
1160 
950 
840 
760 

•3 

•4  ...... 

•5  .  . 

•6  

.7 

•8  

j.q 

i«io  

those  cubes  in  which  the  material  was  pressed  or  rammed  in  the 
moulds  are  here  considered. 

It  appears  that  each  figure  is  the  average  of  two  tests,  but  the 

TABLE  X. 


Brand  of  Cement 

Composition 

Age 

Ult.  Resist, 
in  Lbs. 
per  Sq.  In. 

Cement 

Sand 

Broken  Stone 

Years 

Months 

Alpha  Portland  

! 

2* 

4906 

"             "         .... 

I 

2 

4  —  ^  In.  Trap 

— 

3187 

"         .... 

I 

3 

6 

— 

2070 

"             "          .... 

I 

4 

8 

— 

1499 

"             "         .... 

I 

5 

10 

— 

949 

"             "         .... 

I 

6 

12 

— 

791 

"             "         .... 

I 

2 

1          Trap       / 

2 

— 

2789 



I 

2 

4  <          r£              > 

2 

— 

2549 

" 

I 

2 

|_          i  rap       J 
4—  iyz  In.  Trap 

2 

— 

2466 

"             "         .... 

I 

2 

7 

I 

2 

2406 



I 

2 

f  I*/*  to  3  In.l 
4  1       Pebbles     / 

I 

2 

3589 

"             "         .... 

I 

2 

4{  Brok'nB2rickJ 

I 

2 

3241 

"             "         .... 

I 

3 

6 

I 

I 

2545 

"         .... 

I 

4 

I 

I 

1446 

*Granite  dust. 


composition  of  the  concrete  is  not  clearly  explained;  the  aggre- 
gate is  called  ballast  and  sand.     The  tables  are  inserted  on  ac- 


128 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


count  of  the  interest  attached  to  them,  for  the  experiments  were 
made  in  1867. 

Table  X.  is  taken  from  the  Watertown  Arsenal  Report  for  the 


TABLE  XI. 


Parts  by  Weight  of  Sand  to  Cement 


Ultimate  Crushing  Resistance  per  Sq.  In. 


1:1 

l:l 
1:2 
I:2 
1:3 
l:3 
1:4 


II330 
10390 
9520 
8110 
6140 
6280 
5230 


year  1901,  and  shows  the  ultimate  crushing  resistance  of  12  inch 
cubes,  composed  of  various  proportions  of  cement,  sand  and 
broken  stone. 

TABLE  XII. 


Brand  of  Cement 

Percentage 
of  Water 

Compressive  Strength  in  Lbs.  per 
Sq.  In.  at  an  Age  of— 

7  Days 

1  Month 

3  Months 

Alpha   Portland-    ...               

25 

25 
26.8 
18 
22^ 
25 
30 
25 
29.2 
26.7 
26.7 
18 
28^ 
18 
35.4 
38.7 
36.2 
41.2 
38.7 
39.6 
35-8 
39.2 

6010 
3490 
4280 
5780 
4620 
5560 
5030 
5630 
3510 
2750 
2110 
3860 
1300 
3050 
356 
620 
464 
566 
407 
472 
750 
423 

7340 
5370 
5590 
5990 
5180 
5980 
5620 
6640 
4940 
4030 
2970 
3970 
1790 
3470 
1090 
1130 
790 
1020 
1090 
880 
1360 
840 

8580 
5870 
6310 
6980 
5930 
7730 
6810 
7630 
5510 
4660 
3430 
4490 
2110 
4470 
1530 
1560 
1230 
1420 
1440 
1570 
2220 

mo 

Atlas          "        

Lehigh        "         

Star  Portland  

a           a 

Whitehall  Portland   

Alsen               " 

Silica  Cement  

Bonneville  Improved  Natural  

Newark  &  Rosendale  Natural  

Obelisk       "       

Potomac     "       

Table  XL  gives  the  values  of  the  compressive  resistance  of  ce- 
ment mortar  cubes;  the  tests  were  made  for  the  United  States 
Engineering  Corps  and  are  recorded  in  the  Watertown  Arsenal 


Art.  22.]  ULTIMATE  COMPRESSOR  RESISTANCE.  129 

Report  for  1902.  The  cubes  were  six-inch,  of  Atlas  Portland 
cement,  and  the  sand  used  was  natural,  43.62  per  cent,  passing 
the  No.  30  sieve.  The  cubes  were  each  kept  three  months  in  dry 
air,  fifteen  days  in  water  at  65  degrees  Fahr.,  and  then  in  air  until 
the  date  of  crushing,  almost  two  and  a  half  years  after  making. 
The  compressed  surfaces  were  faced  with  plaster  of  Paris.  The 
rapid  decrease  in  the  ultimate  crushing  resistance  as  the  per- 
centage of  sand  in  the  mixture  increases  is  worthy  of  note. 
These  tests  are  inserted  on  account  of  the  extraordinary  com- 
pressive  strengths  attained.  The  age  of  the  specimens  hardly 
accounts  for  this.  Table  XII.,  which  is  taken  from  the  same  re- 
port, shows  the  ultimate  crushing  strength  of  four-inch  cubes 
of  neat  cement  with  various  brands  of  Portland  and  natural 
cements.  Each  result  is  a  mean  of  from  four  to  five  speci- 

TABLE  XIII. 


Ultimate  Crushing  Strength  in 
Lbs.  per  Sq.  In. 

With  Fine  Sand 

With  Coarse,  Sharp  Sand 

1595 

1  185 
985 

1825 
2145 
1  102 

Selected  Stone,  Containing  Some  Mica.  . 

mens.  All  the  specimens  set  in  air.  In  not  one  of  these  tests 
did  the  ultimate  crushing  resistance  approach  that  shown  in 
Table  XL 

Table  XIII.  gives  the  crushing  strength  of  concrete  composed 
of  one  part  Portland  cement,  three  parts  sand  and  five  parts 
stone,  in  eight-inch  cubes,  as  reported  by  T.  S.  Clark  in  Engi- 
neering News  of  July  24,  1902.  The  table  is  given  for  the  pur- 
pose of  showing  that  different  crushing  strengths  may  be  attained 
by  concrete  with  different  classes  of  stone.  The  cubes  were  kept 
in  air  twenty-four  hours  and  in  water  five  months  before  being 
tested.  The  three  kinds  of  stone  used  were  standard  limestone, 
a  stone  containing  a  large  amount  of  mica  and  which  had  been 
rejected  for  use,  and  a  better  quality  of  this  rejected  stone  con- 
taining less  mica.  It  will  be  seen  that  the  quality  of  both  the 
sand  and  the  stone  bears  intimate  relation  to  the  final  crushing 


130 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


strength,  and  the  rather  vague  opinion  that  a  calcareous  stone  is 
better  than  other  kinds  is  to  a  certain  extent  corroborated. 

Setting  Under  Water— Table  XIV.  is  taken  from  the  Report 
of  the  Watertown  Arsenal  for  1902,  and  furnishes  comparative 
crushing  tests  on  mortars  which  were  allowed  to  set  both  in  air 
and  in  water.  The  majority  of  the  specimens  were  two-inch 
cubes;  larger  size  cubes  are  noted.  The  specimens  which  were 
placed  in  water  were  allowed  to  set  first  one  day  in  air,  and  each 
result  is  an  average  of  from  four  to  five  specimens.  It  will  be 
seen  that  almost  uniformly  those  specimens  which  set  under 
water  attained  the  greater  compressive  strength.  The  table  only 
shows  results  for  one  brand  of  cement,  but  in  all  seven  brands 

TABLE  XIV. 


Brand  of  Cement 

Composition 

Age  in  Days 

Compress- 
ive Strength 
in  Lbs. 
per  Sq.  In. 

Remarks 

Cement 

Sand 

Water 
Per  Ct. 

Air 

Water 

Atlas     

I 
I 
I 

I 

I 
I 
I 
I 
I 
I 
I 

32.0 
32.0 
32.0 
32.0 
32.0 
32.0 
32.0 
32.0 
33.7 
33.7 
33.7 
33.7 
32.0 
32.0 

7 
I 
30 

I 
92 
I 
93 
I 
92 
I 
92 
I 
183 
I 

6 
29 

2540 
2580 
3010 
3470 
3390 
4550 
4100 
6590 
3555 
5000 
3805 
5630 
3370 
4800 

3  In.  Cubes  1 
3  In.  Cubes 
4  In.  Cubes 
4  In.  Cubes 
6  In.  Cubes 
6  In.  Cubes 

to     W 

%*Bz 
-ill 

3»8 

38.- 

»      3T 

91 
92 
91 
91 
182 



were  tested,  for  neat,  1:1  and  1:3  mixtures.     All  the  tests  furnish 
similar  results. 

These  results  do  not  corroborate  those  of  Grant,  previously 
recorded,  in  which  the  specimens  under  water  were  almost  in- 
variably weaker.  Table  XIV.,  taken  in  connection  with  Mr. 
Rafter's  tests,  indicates,  however,  that  mortars  and  concretes 
kept  damp  or  under  water  are  in  general  the  stronger.  The 
latter  is  the  author's  opinion. 

Wet  or  Dry  Concretes — Table  XV.  shows  results  obtained 
from  experiments  made  as  thesis  work  by  J.  W.  Sussex,  published 


Art.  22.] 


ULTIMATE  COMPRESS1VE  RESISTANCE. 


131 


in  the  "Technograph"  of  the  University  of  Illinois  for  1903.  The 
experiments  were  made  to  determine  the  relative  strength  of  wet 
and  dry  concretes.  The  tests  were  made  on  forty-five  six-inch 
cubes  mixed  with  three  different  percentages  of  water  and  broken 
at  the  ages  of  seven  days,  one  month  and  three  months.  The 
concrete  was  composed  of  one  volume  of  Portland  cement,  three 

TABLE  XV. 


Age 

Crushing  Strength  in  Lbs.  per  Sq.  In. 

Dry 

Medium 

Wet 

Lightly 
Tamped 

Heavily 
Tamped 

Lightly 
Tamped 

Heavily 
Tamped 

7  Days    

1200 
1750 
2500 

1340 
I960 
2600 

2280 
2290 
2150 

1330 
2560 
2590 

1040 
2230 
3040 

I  Month    

3  Months  

volumes  of  sand  containing  a  small  percentage  of  fine  gravel  and 
six  volumes  of  crushed  limestone.  Tests  were  made  with  th^ 
three  degrees  of  plasticity  noted,  and  also  with  two  degrees  of 
tamping — light  and  hard.  Each  result  shown  is  an  average  of 
three  tests.  At  the  end  of  three  months  it  will  be  seen  that  the 
wet  concretes  furnished  the  greatest  ultimate  resistance,  although 

TABLE  XVI. 


Kind  of  Cement  and  Sand 

Age  in 
Days 

Ultimate  Compressive  Resistance  in  Lbs. 
per  Sq.  In.  When  Mixed 

Dry 

Medium 

Wet 

Portland  ; 
Natural  ; 
Portland  ; 
Natural  ; 

Bar  Sand  

7 
7 
7 
7 
28 
28 
28 
28 

1330 
1650 
258 
427 
2560 
2360 
481 
708 

1230 
1500 
292 
253 
1890 
2470 
507 
470 

1245 
1450 
328 
138 
1320 
1540 
334 
282 

White        

Bar           

White 

Bar           

White           

Bar           .... 

White       

at  the  end  of  seven  days  and  one  month  the  medium  specimens 
furnished  the  highest  ultimate  resistance,  whether  tamped  lightly 
or  hard. 

T.  L.  Doyle  and  E.  R.  Justice  record  in  "Engineering  News" 
for  July  30,  1903,  the  ultimate  compressive  resistances  of  six-inch 
cubes  made  with  both  Alpha  Portland  and  Hoffman  natural  ce- 


132 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


ments  and  mixed  to  three  different  consistencies.  Two  kinds  of 
sand,  white  sand  and  bar  sand,  were  used,  and  the  stone  was  one- 
inch  trap  rock.  The  ages  of  the  specimens  were  seven  and 
twenty-eight  days.  Table  XVI.  shows  the  results  obtained,  each 
figure  being  an  average  of  five  tests.  It  will  be  seen  that  in  all 
cases  the  dry  specimens  furnished  higher  ultimate  resistances 
than  either  of  the  Other  two  kinds.  The  age  of  the  specimens  is 
not  sufficient  to  show  whether  the  wet  mixtures  would  not  ulti- 
mately be  stronger  than  the  dry. 

High  Temperatures— The  effect  of  high  temperatures  on  ce- 
ment mixtures  has  not  been  studied  to  any  extent  as  yet,  but 
Table  XVIL,  which  is  taken  from  the  Watertown  Arsenal  Re- 
port for  1902,  shows  the  variation  in  the  ultimate  crushing 
strength  of  four-inch  cubes  after  they  had  been  heated  to  differ- 
ent temperatures.  The  age  of  the  cubes  was,  in  most  cases, 

TABLE  XVII. 


Composition 

Ultimate  Crushing  Strength  in  Lbs.  per  Sq.  In. 
After  Heating  to 

Cement 

Sand 

Not 
Heated 

200° 
F. 

300° 
F. 

400° 
F. 

500° 
F. 

600° 
F. 

700° 
F. 

800° 
F. 

900° 
F. 

1  Alpha* 

1 

1 

9167 
12480 
5017 
1867 
3873 
538 
2170 

8830 
14447 

1657 
4043 
491 
2067 

7920 
13853 

1876 
3523 
432 
1953 

9190 
13767 

1966 
3810 

9400 
13910 

1603 
4133 
471 
2063 

9333 
12787 
4313 
1453 
4013 

8217 
12130 
3483 
1496 
3957 
381 
2240 

8060 
9985 
4280 
1400 
3900 

6060 

1185 
2990 
317 
1767 

1  Alphat  

1  Dyckerhoff* 

1  Mankato*  

1        "        t 

1        "        *  

1        "        t 

*Cubes  set  in  air  before  heating.     tCubes  set  in  water  before  heating. 

slightly  over  one  year,  and  they  were  tested,  usually,  about  thirty 
days  after  having  been  heated.  Each  result  is  an  average  of 
three  tests.  It  will  be  seen  that  there  is  practically  no  decrease 
in  strength,  even  up  to  a  temperature  of  600  degrees  Fahr.,  but 
a  decrease  is  shown  for  higher  temperatures. 

Art.  23. — Compressive  Properties. 

Conclusions. 

It  has  seemed  to  the  author  that  the  graphical  method  used  in 
determining  the  straight-line  formula  for  long  columns  was  the 
most  rational  way  to  combine  the  experiments  which  have  been 
recorded  in  the  preceding  pages.  Two  sets  of  straight-line  dia- 


Art.  23.] 


ULTIMATE  COMPRESSIVE  RESISTANCE. 


133 


grams  have,  therefore,  been  prepared,  one  showing  the  relation 
between  ultimate  compressive  stress  and  the  compressive  coeffi- 
cient of  elasticity,  and  the  other  showing  the  relation  between 
ultimate  compressive  resistance  and  the  parts  of  cement  to  aggre- 
gate in  the  mixture.  The  question  of  age  has  been  entirely  ex- 
cluded, since  very  little  material  under  three  months  of  age  was 
used,  and  it  has  previously  been  shown  that  mixtures  do  not  gain 
appreciably  in  strength  after  that  period.  The  figures  otherwise 


f 

/ 

•g 

^ 

1 

•* 

/" 

3 

^ 

"/ 

M 

? 

"/"'' 

1 

03 

/• 

^ 

/ 

z< 

a 

^ 

-  X 

/- 

£ 

^ 

7 

B 

A 

1 

, 

1 

/ 

—  » 

-3 

^ 

*o  Q  000  000 

y 

1 

6 

i 

10 

IX) 

2( 

100 

3000 

Ultimate  Crushing  Resistance  Lbs.  per  Sq.  In. 
FIG.  l.-FROM   BACH'S  TESTS.— TABLE   I.,  ART.  21. 

need  but  little  explanation ;  each  represents  graphically  one  of  the 
tables  which  have  been  recorded  in  the  previous  pages.  Tables 
III.,  IV.,  V.  and  VI.  of  Art.  21  have  not  been  included,  since  the 
values  there  shown  are  not  the  true  or  elastic  coefficients ;  Table 
VII.  has  not  been  included  on  account  of  the  limited  number  of 
tests. 

There  has  also  been  included  in  Figure  8  a  summary  of  the 
tests  made  at  the  Watertown  Arsenal  in  1899  on  twelve-inch  con- 
crete cubes  varying  in  age  from  one  to  six  months.  The  tests 


134 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


were  made  with  five  well  known  brands  of  Portland  cement,  with 
various  mixtures  of  sand  and  stone. 

The  tests  made  by  Messrs.  Derleth  and  Hawkesworth  were  not 
sufficient  in  number  to  enable  their  results  to  be  included  in  a 
figure. 


:  1,000,000 


* 

g  8,000,000 


z 


1000  2000 

Ultimate  Crushing  Resistance  Lbs.  per  sq.  in. 

FIG.  2.— FROM   BACH'S  TESTS.— TABLE   II.,  ART.  21. 

Figures  i  to  9  represent  the  variation  of  the  coefficient  of  elas- 
ticity with  the  variation  of  the  ultimate  compressive  resistance. 
The  equations  of  the  lines  there  shown  are  as  follows,  /  represent- 
ing the  ultimate  compressive  resistance: 

E—i, 520,000+ 1 cjoo/ (Bach)  Fig.  I. 

E—       o        +1820^ (Bach)  Fig.  2. 

£=       o       -\-iooop Fig.  3. 

£=       o       +I090/ Fig.  4. 

E—       o       +i6oo/ (Hatt)  Fig.  5. 

E—       o       +i  57o/ (Austrian)  Fig.  6. 

£=     62,000-j-  794/ (Rafter)  Fig.  7. 

E—       o       +1150^ Fig.  8. 

E=  o       +IOOO/. . . .  (McCaustland)  Fig.  9. 


Art.  23.] 


ULTIMATE  COMPRESSIVE  RESISTANCE. 


135 


Averaging  the  nine  different  numerical  expressions  which 
these  figures  furnish,  it  will  be  found  that  an  average  value  of 
the  compressive  coefficient  of  elasticity  may  be  expressed  by  the 

equation 

^=175,000+1325^, 

in  which  p  represents  the  ultimate  compressive  resistance.     The 

constant  quantity,  175,000,  is  negligible  in  relation  to  the  other 

and  may  be  neglected  with  very 

little   error,   so  that   a   simpler 

form  of  expression  is  the  fol- 

lowing: 


Coefficient  of  Elasticity  in  Lbs.  per  sq.  ii 

i  !  i 

/ 

w 

fyr 

/ 

/ 

X 

2000  3000 

TJlt.  Comp.  Strength  in  Lbs.  per  sq.  in. 
FIG.  3.-EASTERN  EXPANDED  METAL 
CO.'S  TESTS.— FROM  TABLE 
VII.,  ART.  21. 


The  constant  175,000  may  be 
neglected  with  all  the  more 
safety  since  it  depends  mainly 
on  one  series  of  experiments, 
viz.,  Professor  Bach's,  and  in 
these  experiments  the  coeffi- 
cients are  undoubtedly  higher 
than  in  other  cases,  on  account  of  the  repeated  application  of 
every  load. 

In  a  similar  way,  Figures  10  to  15  represent  the  variation  of 
the  ultimate  crushing  resistance  with  the  variation  in  the  ratio  of 
the  cement  to  aggregate;  the  following  equations  are  then  ob- 

tained: 

/=475O  —  250  m  ................  (Bach)    Fig.  10. 

^=5140  —  2380*  ...............  (Rafter)  Fig.  n. 

/=4578  —  289  m  ...............  (Rafter)  Fig.  12. 

^=3835  —  2070*.  .(Watertown,  Table  V.)  Fig.  13. 

^=3440  —  280  m  .........  (McCaustland)  Fig.  14. 

^=5035  —  2i^m  ......  (Watertown,  1899)  Fig.  15. 

Henby's  tests  (page  112)  in  addition  furnish  an  equation  of 

^=4350—  258^. 
The  average  of  all  these  equations  furnishes 

/=4449—  2470*, 
in  which  /  equals  the  ultimate  crushing  resistance  and   m  the 


136 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


9,000,000 

*              X 

X     x. 

C   7,OW,WU 

t 

X     XV  • 

,5  6,000,000 

a 

/ 

/ 

-s 

& 

/ 

- 

*V7 

/ 

1,000,000 

/ 

1000     2000     3000     4000     6000     6000 

Ult.  Comp.  Strength  in  Lbs.  per  sq.  in. 
FIG.  4.— WATERTOWN,   1898,  TESTS.— TABLE  VIII.,  ART.  21. 


5,000,000 

£  5,000,000 

? 
J  4,000,000 

.3 

• 

|  3,000,000 

1 
P 
o  2,000,000 
^ 
3 
i 
01,000,000 

/ 

:/ 

/ 

3 

/:' 

/ 

/ 

/ 

0  1000  2000  3000  1000 

Ult.  Comp.  Strength  in  Lbs.  per  sq.  in. 

FIG.  5. 

HATT'S  TESTS.-TABLES  VI.  AND 
VII.,  PAGES  83  AND   84. 


.55,000,000 

g 

I 

«4,000,000 

3 
B 

X 

/ 

M 

/ 

/x 

X 

1 

2 

•33,000,000 

22,000,000 

B 
.2 

i 

§1,000,000 

I 

,?y 
// 
y 

/ 

/ 

/ 

1000          2000 
TJlt.  Comp.  Strength  Lbs.  per  sq.  in. 

FIG.  6. 

AUSTRIAN  SOCIETY'S  TESTS.-TABLE  IX. 
PAGE   96. 


Art.  23.] 


ULTIMATE  COMPRESS1VE  RESISTANCE. 


137 


teriiiined  for  Intensities  of  Stress  100-GOO  Lbs. 
per  Sq.  In. 
Coefficient  of  Elasticity  in  Ibs.  per  sq.  in. 

1 

X 

3,W 

10,00 

1 

^ 

/ 

X 

X 

s 

* 

f 

'       x 

- 

/ 

JJ 

4 

i> 

t 

<o 

* 

• 

2,<X 

K),00 

0 

* 

1 

/< 

M 

* 

X 

* 

4 

* 

*• 

__ 

/ 

• 

* 

3 

1 

i 

1 

• 

1 

3 

£ 

u 

'c 

Jg 

i 

i 
a 

1000                   aooo                    3000                     woo                   5000 

Ult.  Crush  Load  in  Ibs.  per  sq.  in. 
FIG.  7.-RAFTER'S  TESTS.-TABLE  IX.,  ART.  21. 

5,(K 

0,(XK 

) 

/ 

/ 

4,0(1 

0,(XX 

1 

x 

x  x 

X 

/ 

^x 

/ 

/ 

/ 

' 

* 

/} 

X 

X 

x 

/ 

3.0C 

0,00 

j 

X 

X 

/ 

XX 

x 

/ 

V 

XXX 

x 

*5 

^/ 

? 

X 

x 

XX 

X 

X 

9.0 

0,00 

) 

X 

^ 

/ 

x 

X 

/ 

x 

y  X 

/ 

XX 

/ 

/ 

1,0, 

»,00 

/Tx 

/ 

f  ' 

1,000  2,000  3,000  4,000  5,000 

Ultimate  Crushing  Resistance  in  Pounds  per  Square  Inch 

FIG.  8.— WATERTOWN,  1899,  TESTS  OF  FIVE  WELL-KNOWN  BRANDS 
OF  PORTLAND  CEMENT. 


138 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


ratio  of  aggregate  to  cement.  This  equation  may  be  used  with 
safety  to  determine  the  strength  of  any  mixture,  with  m  between 
the  limits  of  4  and  16. 

The  question  of  the  ultimate  strength  of  cement  mixtures  has 

been   considered   by   the   author 
from  one  point  of  view  only,  viz., 


5,000,000 

3 

* 

s. 
A 

0  3,000,000 

fe 

« 
1  2,000,000 

*o 
|l,000,000 

8 

0 

it 

x 

/ 

•j 

f' 

/ 

1-  *^*x 

/£       H 

/ 

o 

3 

0> 

I10 


1000 


2000 


3000 


iUOO 


\ 


\L 


Ult.  Comp.  Strength  in  Lbs.  per  sq.  in. 

FIG.  9. 

McCAUSTLAND'S  TESTS. 
FROM  TABLE  X.,  ART.  21. 


1UOU  2000  3000  1000 

Ult.  Crush.  Resist,  in  Lbs.  per  sq.  in. 


FIG.   lO.-BACH'S  1896  TESTS,  ON   10-IN. 

CYLINDERS,   10  INS.  HIGH. 

TABLE  II.,  ART.  21. 


the  relation  between  the  cement  to  the  aggregate.  Another 
method  of  dealing  with  this  question  has,  however,  been  studied 
by  R.  Feret  in  Europe,  and  is  being  studied  by  William  B.  Fuller 

in  America;  the  latter's  results 
are    not    yet    published.     This 


'  Parts  of  Aggregate  to  1  of  Cement 

otow-o  OCCIOH^  o  So  < 

X> 

x 

. 

> 

\* 

^ 

f 

V 

S-J> 

<: 

«x 

\ 

^! 

\ 

\ 

X 

S 

^v 

s 

)          1000        2000        3000        1000         5000 
Ult.  Crush.  Resist,  in  Lbs.  per  Sq.In. 

Approximately:  Parts  of 
(Sand  +  Stone)  to  Cement 

0  0.  S  5 

> 

s 

*X, 

fi»x, 

N^ 

\T 

• 

\ 

x 

FIG.  11. 

RAFTER'S  TESTS. 
FROM  TABLE  I.,  ART.  22. 


1000  2000  3000  loo 

Ult.  Crush.  Resist,  in  Lbs.  per  sq.  in. 

FIG.   12. 

RAFTER'S  TESTS. 
FROM  TABLE  IV.,  ART.  22. 


method  considers  not  merely  the  relation  between  the  cement 
and  the  aggregate,  but  also  the  balancing  of  the  entire  mixture. 


Art.  23.] 


ULTIMATE  COMPRESSIVE  RESISTANCE. 


139 


R.  Feret,  for  instance,  has  shown  that  the  ultimate  resistance 
to  compression  of  1 13  mortar  blocks,  in  which  the  sand  was  com- 
posed of  varying  proportions  of  the  three  graded  sizes  of  sand 
which  have  been  previously  noted  in  some  of  his  tests,  varies 
from  some  minimum  value  to  a  value  perhaps  three  times  as 
large,  depending  merely  on  the  proportions  of  the  various  sizes 


0  1000  2000  3000 

Ult.  Crush.  Resist,  in  Lbs. 
per  sq.  in. 

FiG.  13. 

WATERTOWN  TESTS. 
FROM  TABLE  V.,  ART.  22. 


0  1000  2000  3000  MM 

Ult.  Crush.  Strength  in  Lbs.  per  sq.  in. 
FIG    14.— McCAUSTLAND'S  TESTS. 
FROM  TABLE  X.,  ART.  21. 


of  sand.  This  variation  in  strength  is  in  proportion  to  the  varia- 
tion of  the  solid  material  in  the  mass,  the  maximum  value  being 
obtained  when  the  medium  sized  grains  are  eliminated.  This 
was  found  to  hold  true  no  matter  under  what  conditions  the  mor- 


Parts  of  Sand  and  Stone  to  Cement 
eo  c,  S  gfj 

v^ 

Alsen 

"^-, 

•^    l^*^ 

>< 

Say 

or's 

Gei 

man 

ia-^ 

^^^ 

v; 

•  ^"•^, 

^^_ 

/  =  5 

035- 

14  n 

- 

•^ 

^ 

^; 

^ 

as 

x« 

^ 

^ 

^C 

r 

AH 

ha 

""^-^ 

fe 

Si" 

-x 

^ 

^ 

:^-. 

.^ 

-•*- 

-K 

00                                 2000                                 3000                                 1000                                 6000 

Crushing  Resistance  in  Lbs.  per  sq.  in. 

FIG.  15.— WATERTOWN,  1899,  TESTS  ON  FIVE  WELL-KNOWN  BRANDS 
OF  PORTLAND  CEMENTS. 

tars  were  allowed  to  set  and  harden.  Feret  cites  numerous  ex- 
amples, but  Figures  16  and  17  are  characteristic  of  all  his  experi- 
ments. In  this  case  the  percentages  of  the  various  sizes  of  sand 
grains  are  represented  on  the  perpendiculars  erected  on  the  sides 


140 


COMPRESSIVE  PROPERTIES. 


[Ch.  VI. 


of  an  equilateral  triangle,  a  system  of  co-ordination  which  is 
familiar.  The  ultimate  crushing  resistance  of  the  various  mor- 
tars is  marked  at  the  proper  points  within  the  triangle ;  with  these 
points  as  guides,  contour  lines,  representing  mixtures  having  an 
equal  ultimate  resistance,  are  then  drawn. 

Figure  16  shows  very  clearly  how  the  strength  of  the  mixture 
increases  as  the  medium  sized  grains  are  eliminated. 

Figure  17  was  drawn  in  a  similar  manner,  but  represents  the 
relation  of  solid  matter  to  the  total  cubic  contents  in  a  freshly 
mixed  mortar.  The  close  similarity  between  these  two  figures 


1:3  Mortar,  9 
months  in  air, 
3  months  in  sea 
water. 


1:3  Mortar 
(freshly  mixed) 


1420 


2130 


FIG.   17. 


G          4400  F 

Note:    The  letters  G,   M,  F,   indicate  large, 
medium  and  fine  grains  of  sand. 

FIG-   16-  Showing  Proportion  of  Solid  Matter  to  Total  Cubic 

Showing  the  Ultimate  Compressive  Resistances,  Contents  of  Mortars  Mixed  with  Differing  Per- 

in  Lbs.  per  Sq.  In.,  of  Mortars,  Mixed  with  centages  of  Various  Sized  Sand. 
Differing  Percentages  of  Various  Sized  Sand. 

is  noticeable  and  checks  Feret's  conclusion  that  the  .ultimate 
compressive  resistance  varies  in  proportion  to  the  solid  matter 
in  a  specimen.  It  will  require  much  work  of  this  character  in 
order  that  some  definite  conclusions  may  be  obtained. 

Considering  in  general  all  the  tests  which  have  been  tabulated, 
it  may  be  concluded : 

First — That  concretes  in  compression  have  a  point  that  may 
be  termed  the  elastic  limit,  and  its  value  is  between  one-half  and 
two-thirds  of  the  ultimate  resistance. 

Second — That  up  to  this  elastic  limit  the  compressive  coeffi- 
cient of  elasticity  may  have  in  general  a  value  of  1325  times  the 
ultimate  crushing  resistance. 


Art.  23.]  ULTIMATE  COMPRESSIVE  RESISTANCE.  1 4 1 

Third — That,  within  certain  limits,  the  ultimate  crushing  re- 
sistance for  cement  mixtures  over  three  months  old  may  be  ex- 
pressed by  the  equation 

^-4449— 247  m, 

in  which  /  represents  the  ultimate  crushing  intensity  and  m  the 
number  of  parts  of  aggregate  to  one  part  of  cement. 

Fourth — That  concretes  mixed  dry  and  thoroughly  tamped  are 
slightly  stronger  than  those  mixed  wet;  but  in  actual  construc- 
tion work  other  considerations  besides  the  slight  increase  in 
strength  may  offset  this  advantage  which  appears  in  favor  of  the 
dry  concretes. 

Fifth — That  concretes  hardening  under  water  attain  slightly 
greater  ultimate  resistance  than  the  same  mixtures  hardening  in 
air. 

Sixth — That  temperatures  below  600  degrees  Fahr.  do  not  af- 
fect adversely  the  strength  of  concretes. 

It  has  been  shown  that  there  is  no  appreciable  increase  in 
strength  after  the  material  is  three  months  old.  Therefore,  if  it 
is  desired  that  a  concrete  should  possess  ultimately  a  high  value 
of  the  coefficient  of  elasticity,  it  is  possible  to  obtain  it  only  by 
using  richer  mixtures. 

And,  finally,  it  appears  that  the  values  of  the  coefficients  of 
elasticity  for  tension  and  compression  are  practically  equal. 


CHAPTER  VII. 
FLEXURAL   PROPERTIES. 

Art.  24.— The  Theory  of  Flexure  as  Applied  to  Concrete. 

Careful  consideration  must  be  given  to  the  theory  of  flexure  in 
connection  with  concrete  beams  in  flexure.  In  determining  the 
coefficient  of  elasticity  for  flexure  two  conditions  in  the  theory  of 
flexure  are  usually  assumed,  viz.,  that  the  coefficients  of  elasticity 
for  direct  tension  and  direct  compression  are  equal,  and  that  they 
are  constant.  This  is  rarely,  if  ever,  the  case ;  but  in  order  to  de- 
termine the  deflections  of  beams  it  is  necessary  to  make  these  as- 
sumptions in  order  to  determine  the  empirical  value  for  the  flex- 
ural  coefficient  of  elasticity.  It  has  been  shown  that  neither  of 
these  assumptions  holds  precisely  for  concrete,  and  that,  therefore, 


FIG.  1. 

the  value  of  the  coefficient  of  elasticity  which  may  be  deduced  for 
bending  has  no  reasonable  basis;  but  it  seems  to  be  perfectly 
proper  to  determine  it  as  an  empirical  quantity,  since  it  is  a  pos- 
sible way  in  which  to  determine  in  advance  the  deflection  of  these 
concrete  beams. 

The  quantity,  which  is  usually  called  the  modulus  of  rupture, 
or  the  extreme  fib're  stress  at  rupture,  is  probably  as  correct  a 
quantity  for  concrete  as  in  the  case  of  any  other  material,  even 
such  as  steel  or  wrought  iron.  This  modulus  of  rupture  is  de- 


. 


Art.  24.]  THE  THEORY  OF  FLEXURE.  143 

termined  from  the  theory  of  flexure,  on  the  assumption  that  the 
stress  in  any  fibre  at  a  section  of  the  beam  varies  directly  as  the 
distance  from  the  neutral  axis  of  the  beam.  At  the  time  of  rup- 
ture this  does  not  hold  true  for  steel,  for  wood,  for  concrete  or 
for  any  substance  whatsoever.  This  value,  therefore,  is  not  cor- 
rect for  any  material,  but  it  is  of  the  greatest  value  in  the  design 
of  beams. 

The  writer  has  discussed  the  analytic  treatment  of  concrete 
beams  fully  in  another  place,*  and  it  is  therefore  unnecessary  to 
repeat  that  treatment  here  ;  but  the  following  analysis  for  finding 
the  deflection  of  a  beam  composed  of  a  material  having  unequal 
coefficients  of  elasticity  for  tension  and  compression  is  of  con- 
siderable interest  on  account  of  the  simplicity  of  the  final  equa- 
tions. Let  Figure  i  represent  the  cross  section  of  a  beam  of 
such  a  material,  NN  representing  the  neutral  axis  as  determined 
in  some  possible  way. 

The  following  notation  will  be  used  : 

/=intensity  of  stress  at  units  distance  from  NN; 

2=the  distance  of  any  elementary  area  dA,  from  NN; 

«=the  unit  strain  corresponding  to/; 

EI  and  .fic^the  coefficients  of  elasticity  of  the  materials  for  ten- 

sion and  compression  respectively; 
At  and  ^4C—  the  areas  at  any  section  which  carry  tension  and 

compression  respectively; 
It  and  /c=the  moments  of  inertia  of  At  and  Ac  respectively  about 

NN  as  an  axis. 

From  the  general  theory  of  flexure,  the  moment  of  the  stress 
acting  on  the  differential  area  dA,  distant  z  from  NN,  about  that 
axis  is  : 

z  .  p  .  dA  .  z=£fji  .  z*.  dA. 

The  differential  internal  moment,  integrated  over  the  entire 
section,  becomes  equal  to  M,  the  external  moment: 


/d,  /~fy—  ^i 

z\dAc+Et.p\         z\dAt    .     .     .     (i) 
fj  •/    O 

/«.f*  .    .....    (2) 


*  Trans.  Am.  Soc.  C.  £.,  Dec.,  1903. 


144  FLEXURAL  PROPERTIES.  [Ch.  VII. 

But  ft=z  —  =:  —  —  ,  if  p  represents  the  radius  of  curvature  of  the 
P      do? 

neutral  axis;  therefore 


dxi 

M 
or,  -  —  —        -    .......     (3) 

do?       Eclc+Etlt 

If  £c=£t,  then  --  =  —  where   /  represents  the  moment  of 
do?     El 

inertia  of  the  entire  section  about  NN. 

By  the  aid  of  Eq.  3,  it  would  be  possible  to  determine  both  Et 
and  EC,  by  means  of  the  deflections  found  under  two  different 
loads,  provided  the  position  of  the  neutral  axis  could  be  deter- 
mined. To  determine  the  neutral  axis  it  becomes  necessary  to 
know  in  advance,  or  to  assume,  both  Et  and  Ec.  If  assumed, 
the  correctness  of  these  values  must  then  afterward  be  checked 
by  means  of  the  deflections. 

To  pass  through  such  a  procedure  becomes  a  tedious  task, 
more  especially,  as  has  been  shown,  that  Et  and  Ec  for  concrete 
do  not  differ  greatly,  if  at  all.  In  all  his  work  the  author  there- 
fore has  calculated  the  apparent  flexural  coefficient  of  elasticity, 
assuming  Et  equal  to  Ec. 

Since  concrete  beams  show  permanent  deflections  under  com- 
paratively light  loads,  it  also  becomes  necessary,  as  in  the  case  of 
pure  compression,  to  distinguish  between  the  elastic  coefficient 
and  one  calculated  from  the  total  strains  only. 

Art.  25.  —  Flexural  Coefficient  of  Elasticity. 

Table  I.  and  Figure  i  are  taken  from  a  paper  by  the  author  and 
recorded  in  the  Transactions  of  the  American  Society  of  Civil  En- 
gineers, 1903.  The  table  shows  the  values  of  the  flexural  coeffi- 
cient of  elasticity  and  of  the  extreme  fibre  stress  for  concrete 
beams  4x4  inches  X36  inches  span,  tested  to  destruction  by  a 
centre  load.  The  table  is  of  interest  on  account  of  the  age  of  the 
specimens  tested,  which  was  seven  and  one-third  years.  The 
mixtures  used  are  given  in  the  table;  the  sand  was  Cow  Bay,  L.  I., 


Art.  25.] 


FLEXURAL  COEFFICIENT  OF  ELASTICITY. 


145 


and  the  gravel  was  rounded,  varying  in  diameter  from  \  to  2.\ 
inches ;  it  was  well  washed  before  being  used. 

Figure  i  shows  the  deflections  at  the  centres  of  the  different 
specimens.     The  deflections  of  each  bar  are  represented  by  two 


Load  at  Center,  in  Pounds  Load  at  Center,  in  Pounds 

iiiiiiiiiiiiiliil  111111111 

\ 

600 
500 
400 
300 
200 
100 

1100 
1000 
900) 
800 
700 
600 
500 
400 
:',00 
200 
100 

F 

"'i 

RESULTS  OF  TESTS  OF 
CONCRETE  AND  MORTAR  BEAMS 

Corapositiou  of  Bars  or  Beams. 
A  =  1  Aalborg  cement,  2  sand  and  4  gravel 
B  =  1  Atlas  cement  and  3  sand. 
C^=  1  Alsen  cement,  3  sand  and  5  gravel. 
D  =  1  Alsen  cement  and  2  sand. 
The  subscript  figures  refer  to  the  tests  in 
Table  No.l. 

B  '/ 

\ 

<M  ' 

1 

i  # 

/ 

*7 

'  i 

/ 

/ 

1 

I 

^ 

J_ 
/ 

i 

/ 

All  Uars  4.12  Ins.  high 
and  4.06  ins.  vide. 
Spans  for  each  =16  ing. 

The  Deflections  of  each  bar  are  represented  by 
two  curves;  that  to  the  left  shows  the  sets  when 
the  load  at  the  given  point  was  entirely  removed 

__ 

^ 

1 

? 

I/ 

/ 

\ 

J/ 

/°" 

4 

} 

0 

. 

2 

/'CT 

7\^ 

<^> 

r 

i 

/ 

/ 

/ 

/>• 

J 

q/ 

/ 

/* 

/ 

/ 

^ 

^ 

^ 

All  Bars  4.12  ins.  high 
and  4.06  ins.  *ide. 
Span  for  0  =  36  ins. 
Span  for  Cj=  16  ina. 
Span  for  Oi=  16  ins. 

/ 

i 

// 

/' 

*w. 

/ 

/ 

«; 

I  , 

; 

I 

I 

/ 

/ 

1 

1 

/ 

/ 

2 

/ 

H 

/ 

j 

3 

2 

r/ 

3 

1 

/ 

? 

/ 

• 

a 

// 

? 

j 

> 

1 

/ 

1 

y 

// 

if 

1 

X 

J 

/ 

l 

/ 

'« 

/ 

t 

/ 

x' 

I 

/ 

/ 

// 

• 

s* 

^ 

i  , 
/ 

{  ^ 

& 

k 

•'/ 

^ 

/ 
£ 

z. 

All  B, 
ai 

1 

»rs  4.12  ina.  high 
d  4  ins.  wide. 
Q  for  B  =  30  ins. 
nforB^lCins. 
n-teBgieisfe. 

1 

I* 

& 

2 

* 

All  Bars  4.  10  ins.  high 
and  4.15  'ins.  wide. 
Span  for  D=  36  Ins. 
Span  for  D!=--  16  ins. 
Span  for  D?=  16  ins. 

k 

X 

^ 

^ 

:  i 

^ 

1     1     1 

0.006         0.010         0.014          0.018         0.022 
Deflection  at  Center,  in  Inches 

FIG.  1. 


0.002        O.OOG         0.010        0.011         0.018 
Deflection  at  Center,  in  Inches 


curves  lettered  with  the  same  subscript.  The  curve  to  the  left 
shows  the  set  when  the  load  at  that  given  point  was  entirely  re- 
moved. It  was  found  that  the  true  or  elastic  coefficients  of  elas- 


146 


FLEXURAL  PROPERTIES. 


[Ch.VII. 


ticity,  calculated  in  the  way  which  has  already  been  explained, 
gave  constant  values  for  the  coefficient  for  any  one  specimen  al- 
most up  to  the  breaking  load.  The  table  shows  that  neither  the 
coefficient  nor  the  ultimate  strength  shows  any  remarkable  in- 


TABLE  I. 


Bar 

Age 
in 
Years 

Span 
in 
Inches 

Section  of  Bar 
in  Inches 

Coefficient  of 
Elasticity  in 
Lbs.  per  Sq.  In. 

Extreme  Fibre 
Stress  in 
Lbs.  per  Sq.  In. 

Depth 

Width 

A 

7  4 

Of. 

419 

A  Ofi 

A,.... 

7.4 

16 

4.12 

4.06 

1,591,000 

278 

A,.... 

7.4 

16 

4.12 

4.06 

1,102,000 

315 

B  

7 

36 

4  12 

4  00 

2  122  000 

606- 

B!,... 

7 

16 

4.12 

4.00 

2,440,000 

636 

B?.... 

7 

16 

4.12 

4.00 

1,220,000 

530 

C.... 

7 

36 

4.12 

4.05 

1,315,000 

247 

C,.... 

7 

16 

4.12 

4.05 

387,000 

229 

c?.... 

7 

16 

4.12 

4.05 

1,023,000 

208 

D.... 

7.3 

36 

4.10 

4.15 

1,165,000 

294 

D,.... 

7.3 

16 

4.10 

4.15 

597,000 

415 

D2.... 

7.3 

16 

4.10 

4.15 

597,000 

346 

Bars  A=l  Aalborg  cement,  2  sand  and  4  gravel. 
"      B=l  Atlas  cement  and  3  sand. 
"     C=l  Alsen  cement,  3  sand  and  5  gravel. 
"     D=l  Alsen  cement  and  2  sand. 


crease  for  very  old  specimens.  They  may  increase  for  beams 
less  than  one  year  old,  but  for  bars  of  the  age  shown  in  the  table 
neither  of  the  constants  shows  any  material  increase. 

In  discussing  these  experiments  Professor  E.  J.  McCaustland 


TABLE  II. 


Specimen  No. 

Brand 

Coefficient  of  Elasticity 
in  Lbs.  per  Sq.  In. 

Extreme  Fibre  Stress 
in  Lbs.  per  Sq.  In. 

C"               *        \         \s 

571 
357 
238 
190 
623 
618 
452 

2             

1,384,000 
600,000 
460,000 
1,219,000 
1,582,000 
920,000 

7 

<              ,, 

4  .  . 

<              tt 

^  .  . 

Empire  Portland-  .  . 

6  

7  

records  in  the  same  Transactions  some  experiments  made  by  him 
on  neat  cement  beams  2x2f  inches  deep  X24  inches  span,  one 
year  old,  tested  by  centre  loads. 
Table  II.  shows  results  of  the  constants  determined  in  the  same 


Art.  25.]  FLEXURAL  COEFFICIENT  OF  ELASTICITY.  147 

manner  as  in  the  preceding  table.  It  is  to  be  noted  that  the  co- 
efficient of  elasticity  increases  with  the  increase  of  the  extreme 
fibre  stress.  The  stress-strain  curves  shown  by  Professor  Mc- 
Caustland  are  exactly  similar  to  those  of  Figure  I  and  need  not 
be  reproduced. 

In  the  same  discussion  Professor  G.  Lanza  records  results  of 
experiments  on  one  plain  and  twenty-six  reinforced  concrete 
beams  8x12  inches  xn  foot  span. 

At  this  point  it  is  only  necessary  to  introduce  the  results  of  the 
neat  specimen,  since  the  others  must  be  analyzed  by  a  theory  of 
flexure,  which  is  not  a  part  of  the  present  discussion. 

For  the  plain  concrete  beam,  whose  age  was  forty  days,  the 
value  of  the  extreme  fibre  stress  was  found  to  be  170  pounds  per 
square  inch,  the  composition  of  the  concrete  being  one  part  Port- 
land cement,  three  parts  sand,  four  parts  of  trap  rock  passing  a 
one-inch  ring  sieve,  and  two  parts  01  the  same  rock  passing  a  -J- 
inch  ring  sieve,  all  proportions  being  measured  by  volume. 

Jules  A.  Coelos  and  R.  A.  W.  Carleton,  graduating  students  of 
the  Civil  Engineering  course  at  Columbia  University,  1904,  per- 
formed during  the  winter  of  1903-04  an  extended  series  of  tests 
on  plain  and  reinforced  concrete  beams  6x6  inches  in  cross  sec- 
tion, tested  on  a  span  of  36  inches.  The  materials  which  were 
used  were  exactly  the  same  as  those  used  in  the  direct  tension 
and  compression  tests  recorded  previously  on  page  84  in  the  ex- 
periments of  Messrs.  Derleth  and  Hawkesworth,  and  need  no 
further  explanation. 

The  loading  was  either  a  single  centre  loading  or  was  placed 
at  two  points  symmetrically  distant  from  the  centre  of  the  span. 
The  deflections  were  read  in  the  centre  of  the  beam  in  the  same 
manner  as  the  tests  which  were  recorded  in  Table  L,  and  the  co- 
efficient of  elasticity  was  calculated  as  the  true  coefficient. 

Only  the  plain  concrete  beams  are  given  in  Table  III.  Tests 
of  the  ultimate  shearing  resistance  of  the  bars  were  made  after 
they  had  been  broken,  and  these  values  are  also  given  in  the 
table. 

W.  L.  Brown  has  recorded  in  the  Proceedings  of  the  Institu- 
tion of  Civil  Engineers,  1898-1899,  a  series  of  tests  on  cross 


148 


FLEXURAL  PROPERTIES. 


[Ch.VII. 


bending  of  neat  cement  and  mortar  mixtures.  The  size  of  the 
specimens  was  always  2  inches  deep  by  i  inch  wide  by  30  inches 
span.  Three  kinds  of  sand  were  used — a  good  ordinary  coarse 
red  sand,  well  washed;  a  poor  argillaceous  fine  sand,  unwashed, 
and  a  fine  Laxey  gravel,  which  was  really  a  very  coarse  sand. 

Two  sets  of  experiments  were  made,  using  two  brands  of  ce- 
ment. The  deflections  were  measured  at  the  centre  of  the  beams, 
the  loads  being  placed  at  the  same  points.  The  coefficients  of 
elasticity  were  determined  from  the  formula  of  the  common  the- 
ory of  flexure  and  calculated  between  the  extreme  limits  of  stress 
obtained.  The  breaking  load  varied  from  a  centre  load  of  5  to  35 

TABLE  III.— FLEXURAL   TESTS    ON    1:3:5    PORTLAND   CEMENT 
CONCRETE  BEAMS,  6x6x36  INCH  SPAN. 


No. 

Age  in 
Days 

Loading 

Coefficient  of 
Elasticity  in 
Lbs.  per 
Sq.  In. 

Net  Fibre 
Stress 
Lbs.  per  Sq.  In. 

Shearing  Tests 
Shearing  Intensity  in  Lbs. 
per  Sq.  In. 

At  First  Crack 

At  Failure 

I      

127 
128 

128 
125 
141 

121 

At  2  Points 
At  Centre 

1,118,900 
1,002,300 

1,440,900 
2,161,500 
1,012,500 

1,205,500 

170 
218 

189 
225 
148 

223 

180 
/  118 

1153 

101 

167 
f    97 
I    86 

1256 
1  196 
1  178 
1  180 
f  168 
1255 
214 

/330 

1226 

2  

5   . 

7  
8   

21  

pounds.  On  account  of  the  small  sizes  of  the  specimens  and  on 
account  of  some  ambiguity  in  the  methods  of  calculation,  it  has 
been  thought  better  not  to  give  here  in  detail  the  experiments 
themselves,  but  merely  Mr.  Brown's  general  conclusions: 

That  E  is  greater  for  neat  cements  than  for  mortars;  that  E 
varies  inversely  with  the  amount  of  sand  in  a  specimen;  that  the 
quality  of  sand  affects  E,  but  not  considerably,  but  that  age  does 
increase  E  to  a  measurable  extent. 

Some  experiments  on  the  coefficient  of  elasticity  of  concrete 
beams  have  been  recorded  by  Durand-Claye  in  "Annales  des 
Fonts  et  Chaussees,"  1888,  and  are  here  shown  in  Table  IV. 
Tests  were  made  on  seven  bars;  six  were  neat  Portland  cement 


II 

3   Z 


S  s 

5  a 


Art.  26.] 


MODULUS  OF  RUPTURE  IN  BENDING. 


149 


and  one  was  1:2  mortar.  The  prisms  were  approximately  1.2 
inches  square,  tested  on  a  span  of  39.4  inches;  it  does  not  appear 
that  the  sets  remaining  after  the  loads  were  removed  were  meas- 
ured, so  that  the  values  given  in  the  table  are  not  the  elastic 
coefficients. 

It  is  seen,  therefore,  that  the   coefficient  increases  with   the 
value  of  the  extreme  fibre  stress,  and  acts,  therefore,  similarly  to 

TABLE   III. 


Composition  in 
Parts  by  Weight 

Age  When 
Tested 

How  Kept 

Coefficient  of 
Elasticity  in 
Lbs.  per  Sq.  In. 

Extreme 
Fibre 
Stress  in 
Lbs.  per 
Sq,  In. 

Net  Tensile 
Resistance 
of  Similar 
Specimens 
in  Lbs. 
per  Sq.  In. 

Cement 

Sand 

Neat 
I 



5  to  6  Weeks 

6  Months 
2 

Under  Water 
In  Air 

3,380,000 
3,370,000 
2,810,000 
3,410,000 
3,340,000 
3,860,000 
3,410,000 

1000 
950 
781 
1020 
923 
1090 
370 

880 
823 
667 
824 
780 
950 
270 

2 

pure  tension  or  compression;  its  value  does  not  appear  to  differ 
greatly  from  that  found  in  those  cases. 

Art.  26. — Modulus  of  Rupture  in  Bending. 

Table  I.  gives  the  results  of  flexural  tests  on  in  concrete 
beams,  as  reported  by  E.  S.  Wheeler  in  the  Report  of  the  Chief 
of  Engineers,  U.  S.  Army,  for  1895,  p.  2922.  The  specimens 
were  all  10  inches  square  and  4^  feet  long,  broken  on  a  4- foot 
span,  with  a  centre  load.  In  general  the  bars  were  kept  covered 
with  moist  earth,  awaiting  the  time  of  breaking.  The  age  of  the 
beams  was  between  six  months  and  two  years.  It  will  be  seen 
that  there  is  considerable  difference  in  the  strength  of  those 
beams  when  the  stone  used  was  sandstone  or  limestone.  In 
almost  every  case  the  limestone  furnished  higher  values  of  the 
modulus  of  rupture.  The  tests  included  beams  mixed  with  both 
Portland  and  natural  cements.  Figs,  i  and  2  are  plotted  from  the 
table,  the  ordinates  being  the  extreme  fibre  stresses  of  the  beams 
and  the  abscissae  being  the  ratios  by  volume  of  the  aggregate 
(the  sand  and  stone)  to  the  cement.  No  attention  was  paid  in 


150 


FLEXURAL  PROPERTIES. 


[Ch.VII. 


the  figures  to  the  difference  in  age  of  the  various  specimens,  but 
tests  Nos.  98  to  in  were  not  plotted.    A  straight  line  was  drawn 


20 

; 

V 

x 

x 

*  J! 

\ 

*x, 

» 

N 

% 

x^ 

x 

X 

^ 

^ 

x 

x 

0  2  ,« 

X 

X 

X 

-V 

,v 

x 

* 

if 

,?- 

^^ 

^ 

l!^- 

S^ 

xX 

' 

1 

\ 

' 

' 

O  ri 

X 

^ 

x. 

^ 

X 

5  a- 

x 

^ 

^ 

x 

3s" 

\ 

> 

« 

X 

x 

x 

S      a 

0 

i 

X) 

20 

0 

L-.( 

X) 

1C 

10 

5( 

)() 

00 

0 

71 

K) 

7 

30 

Extreme  Fiber  Stress  in  Ifts.  per  sq.  in. 
FIG.  1.— TESTS  ON  PORTLAND  CEMENT  BEAMS  BY  E.  S.  WHEELER. 

to  average  as  nearly  as  possible  the  results  as  plotted;  the  equa- 
tion of  the  lines  for  Portland  cement  mixtures  was  found  to  be : 

*— 840— 37.67 
and  for  natural  cements 

^=526 — 42.67. 

Using  these  lines  as  a  basis,  it  will  be  seen  that  the  greatest  pos- 
sible modulus  of  rupture  which  can  be  obtained  is  for  the  neat 


B      , 

x 

E 

•<  ,  11 

•v 

s 

> 

K 

~    %       0 

•>». 

"^ 

=  5  ! 

^ 

-v. 

si  ; 

^-1 

"-5 

Vf- 

Srr     ' 

V* 

* 

* 

^ 

y^ 

f\\ 

»2      B 

y 

^ 

^ 

X 

=  ^0 

••«v 

3  oo    o 

X 

x 

>~        0 

* 

«     1 

^0  100  200  300  400  500 

^  Extreme  Fiber  Stress  in  Ibs.  per  sq.  in. 

FIG.  2.— TESTS  ON  NATURAL  CEMENT  BEAMS  BY  E.  S.  WHEELER. 

cement,  and  is  respectively  840  and  526  Ibs.  per  square  inch  for 
the  Portland  and  natural.    These  values  decrease  steadily  as  the 


Art.  26.] 


MODULUS  OF  RUPTURE  IN  BENDING. 


151 


TABLE   I. 


Proportionate  Parts 
by  Volume 

Kind  of  Stone 

Age 
When 
Broken 

Wt.  per  Cu. 
Ft.  of  Con- 
crete When 
Broken 

Extreme 
Fibre  Stress 
in  Lbs. 
per  Sq.  In. 

Cement 

Sand 

Gravel 

22  

1  Portland 

1.24 

3.0 

Limestone 

2  Years         153 

597 

23  

1.67 

4.0 

155 

551 

24-    ... 

" 

1.67 

4.0 

** 

6  Months 

155 

465 

25  

1  Natural 

1.78 

4.18 

Sandstone 

lYear 

136 

124 

26  

1.78 

4.18 

Limestone 

148 

150 

27  

" 

1.78 

4.18 

" 

" 

140 

242 

28  

' 

2.16 

4.18 

Sandstone 

" 

140 

94 

29  -.-. 

" 

2.16 

4.18 

Limestone 

" 

141 

96 

30  

" 

2.16 

4.18 

" 

139 

204 

31  

1  Portland 

3.14 

7.61 

Sandstone  and  Gravel 

" 

144 

219 

32  

" 

3.14 

7.61 

Limestone  and  Gravel 

" 

151 

239 

33  

" 

3.14 

7.61 

Gravel 

" 

150 

192 

34  

" 

3.14 

7.61 

Limestone  and  Gravel 

" 

143 

185 

35  

" 

3.12 

9.52 

Gravel 

" 

139 

139 

36  

H 

3.12 

9.52 

Limestone 

" 

141 

169 

37  

" 

3.07 

9.52 

" 

" 

144 

283 

38  

" 

3.08 

7.61 

« 

" 

148 

422 

39  

" 

3.08 

6.34 

M 

" 

148 

374 

40  

" 

3.07 

9.52 

H 

" 

143 

285 

41  

" 

3.08 

7.61 

M 

" 

139 

279 

42  

" 

3.18 

11.42 

(( 

" 

145 

247 

43  

" 

3.18 

6.34 

" 

" 

140 

319 

44  
45  

1  Natural 

3.18 
2.30 

11.42 
8.23 

Limestone  with  Screenings 
Gravel 

M 

141 
150 

298 
120 

46  

2.27 

6.86 

" 

151 

74 

47  

" 

2.25 

10.17 

" 

" 

146 

110 

'48  

" 

2.27 

6.86 

Sandstone 

" 

146 

123 

49  

" 

2.25 

10.17 

" 

131 

74 

50  

" 

1.87 

5.33 

" 

" 

138 

181 

51  

" 

1.87 

5.33 

H 

" 

139 

214 

52  

" 

1.87 

5.33 

" 

" 

138 

175 

53  

1  Portland 

4.16 

13.9 

« 

M 

133 

177 

54  

4.16 

13.9 

" 

" 

132 

213 

55  

" 

4.16 

13.9 

" 

" 

132 

204 

56  
57  

1  Natural 

1.50 
1.50 

5.38 
5.38 

M 

(( 

" 

140 
136 

194 
210 

58-.   -. 

M 

1.50 

5.38 

» 

" 

59  
60  

1  Portland 

5.2 
5.2 

13.2 
13.2 

M 

H 

135 
141 

193 
221 

61  

• 

5.2 

13.2 

« 

" 

62  

1  Natural 

1.12 

4.15 

" 

" 

140 

275 

63  

1.12 

4.15 

M 

M 

137 

306 

64--.- 

" 

1.12 

4.15 

M 

" 

— 

— 

65  

1  Portland 

2.1 

11.1 

ii 

" 

132 

255 

66  

" 

2.1 

11.1 

" 

" 

134 

269 

67  

" 

2.1 

11.1 

" 

" 

— 

68  

" 

4.16 

12.4 

" 

20  Months 

— 

357 

69  

" 

4.16 

12.4 

" 

"  . 

— 

288 

70  

" 

3.12 

12.4 

" 

" 

— 

297 

71  

" 

3.12 

12.4 

u 

" 

— 

351 

72  

" 

2.08 

12.4 

" 

" 

— 

326 

73  

" 

2.08 

12.4 

" 

" 

— 

345 

74  

" 

1.04 

12.4 

" 

" 

— 

310 

75  

" 

1.04 

12.4 

" 

" 

— 

288 

76  

" 

0.00 

2.09 

" 

19  Months 

— 

582 

77  

" 

0.00 

2.09 

" 

— 

605 

78  

" 

1.04 

3.76 

" 

" 

— 

652 

79  

" 

1.04 

3.76 

" 

H 

— 

727 

80  

" 

2.08 

5.57 

" 

" 

— 

488 

81  

" 

2.08 

5.57 

II 

" 

— 

588 

82   •••• 

" 

3.12 

7.71 

" 

" 

— 

513 

83  

" 

3.12 

7.71 

" 

" 

— 

465 

84  

" 

4.16 

9.86 

" 

" 

—          376 

85  

" 

4.16 

9.86 

" 

" 

382 

152 


FLEXURAL  PROPERTIES. 


[Ch.  VII. 


TABLE  \.— Continued. 


Proportionate  Parts 
by  Volume 

Kind  of  Stone 

Age 
When 
Broken 

Wt,  per  Cu. 
Ft.  of  Con- 
crete When 
Broken 

• 

$      c 

o  fc     — 
EW«:T 
«£j=co 

££*£ 

Cement 

Sand 

Gravel 

86..     . 

1  Portland 

5.20 

11.93 

Sandstone 

19  Months 



285 

87.- 

5.20 

11.93 

** 

— 

283 

88-. 

" 

6.24 

13.80 

" 

" 

— 

288 

89-- 

<i 

6.24 

13.80 

" 

— 

237 

90  - 

1  Natural 

0.75 

3.05 

" 

— 

363 

91-. 

" 

0.75 

3.05 

" 

— 

477 

92-- 

1.50 

4.06 

1 

— 

313 

93-. 

1.50 

4.06 

' 

— 

351 

94-. 

2.25 

5.90 

' 

— 

206 

95-. 

2.25 

5.90 

' 

— 

274 

96.. 

3.00 

7.40 

1 

— 

187 

97.- 

3.00 

7.40 

' 

— 

185 

98*. 

1  Po  tland 

2.08 

5.64 

8  Months 

131 

68 

99*. 

2.08 

5.64 

16  Months 

159 

100.- 

2.08 

5.64 

" 

— 

202 

101. 

2.08 

5.64 

8  Months 

146 

110 

102t- 

2.08 

5.64 

16  Months 

245 

103t. 

2.08 

5.64 

8  Months 

143 

145 

104t. 

2.08 

5.64 

" 

138 

142 

105t 

2.08 

5.64 

16  Months 

— 

227 

106.- 

2.08 

5.64 

8  Months 

142 

131 

107.- 

2.08 

5.64 

16  Months 

— 

223 

108§. 

2.08 

5.64 

8  Months 

144 

242 

109S 

2.08 

5.64 

16  Months 

351 

noir.... 

2.08 

5.64 

8  Months 

145 

203 

mir.... 

2.08 

5.64 

" 

16  Months 

273 

Nos.  98-1 1 1  not  plotted  in  Fig.  1.        *Frost  in  stone.        tWater  100  deg.  Fahr. 
156  deg.  Fahr.        §Water  contained  18.75%  salt.        HWater  contained  12.5%  salt. 


JWater 


sand  and  stone  are  increased,  until  they  become  zero  for  a  mix- 
ture of  22.5  parts  and  12.5  parts  for  the  Portland  and  natural 
respectively.  A  straight-line  formula  of  this  kind  furnishes  a 
convenient  analytical  guide  to  show  the  variation  in  strength  of 
different  cement  mixtures. 

Table  II.  is  taken  from  tests  reported  by  Mr.  H.  'Von  Schon, 
in  the  Transactions  of  the  American  Society  of  Civil  Engineers 
for  December,  1899,  and  shows  results  of  Portland  cement  con- 
crete beams  6x6x18  inches  span,  tested  to  destruction  by  flexure. 
The  average  age  of  the  specimens  which  set  in  air  was  about  60 
days.  The  sand  was  St.  Mary's  River ;  the  broken  sandstone  was 
native  Potsdam  and  the  broken  boulder  stone  was  granitic.  The 
broken  stone  all  passed  through  a  ij-inch  ring  and  was  retained 
on  a  i -inch  ring. 

The  table  shows  five  different  mixtures,  varying  in  richness  of 
cement  from  the  "D"  mixture  down  to  the  "A"  mixture.  It 
will  be  seen  that  the  richer  mixtures  always  gave  the  highest 


Art.  26.] 


MODULUS  OF  RUPTURE  IN  BENDING. 


153 


3io 


results  for  ultimate  fibre  stress.    The  "E"  mixtures,  which  were 
the  leanest  of  the  series,  also  contained  a  small  percentage  of 
lime.     In  no  case  did  such  a  mix- 
ture attain  the  strength  of  any  of 
the  others.     Figure  3  shows  the  re- 
sults of  the  table  in  graphic  form.   J 
It  is  seen  that  no  empiric  equation   | 
can  express  these  values.  * 

Table  III.  is  compiled  from  Re-   I 
ports  of  the  Boston  Transit  Com-   |  \ 
mission   for  the   years    1901,    1902 
and  1903,  and  shows  the  ultimate 
fibre  stress  of  Portland  cement  concrete  beams  when  tested  to 
destruction.     The  specimens   represented  in  the   first   six   lines 

TABLE  II.— PORTLAND  CEMENT  CONCRETE  BEAMS, 
6x6xI8-INCH  SPAN. 


! 


100  200  300  tOO 

Modulus  of  Rupture  in  Lbs.  per  sq.  in. 

FIG.  3. 


Brand  of 
Cement 

Kind  of 
Broken  Stone 

Mixture 

No.  of 
Tests 

Ultimate  Fibre  Stress—  Lbs.  per  Sq.  In. 

Maximum 

Mean 

Minimum 

E 

Sandstone 
Boulder  Stone 
Sandstone 
Boulder  Stone 

A 
B 
C 
D 
E 
A 
B 
C 
D 
E 
A 
B 
C 
D 
E 
A 
B 
C 
D 
E 

2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 
2 

178 
225 
288 
329 
108 
354 
358 
390 
420 
350 
181 
183 
266 
328 
195 
390 
423 
410 
411 
332 

176 
217 
280 
325 
102 
326 
328 
373 
410 
330 
169 
175 
262 
308 
182 
347 
406 
392 
393 
322 

174 
209 
272 
321 
97 
298 
299 
356 
400 
310 
158 
167 
258 
288 
169 
204 
390 
374 
375 
312 

E  

E 

E 

E  

E 

E 

E  
E  
E  
R  
R  
R    

R  

px    

R  

p 

p 

p 

Mixture  A=l  cement,  2.4  sand,  5.3  broken  stone. 
Mixture  B=l  cement,  2.4  sand,  4.8  broken  stone. 
Mixture  C=l  cement,  2.4  sand,  4.4  broken  stone. 
Mixture  D=l  cement,  2.4  sand,  4.0  broken  stone. 
Mixture  E=l  cement,  0.3  lime,  3.1  sand,  5.3  broken  stone. 


were  hand  mixed;  the  next  four  were  machine  mixed;  but  the 
method  of  mixing  the  last  two  is  not  stated.     The  sand  was 


154 


FLEXURAL  PROPERTIES. 


[Ch.  VII. 


clean  and  sharp;  the  crushed  stone  was  trap  rock,  i  to  2\  inches 
in  size ;  and  the  stone  dust  was  finely  crushed  stone,  varying  from 

TABLE  III.— PORTLAND  CEMENT  CONCRETE  BEAMS, 
6x6x30-INCH  SPAN. 


Composition 

09 

g 

by  Volume 

2 

Ultimate  Fibre  Stress 

Age 
in 

03 

c 

in  Lbs.  per  Sq.  In. 

Remarks 

— 

c 

«« 

• 

> 

JSg 

Days 

o£ 

1 

§3 
wQ 

O 

81 

CQcfl 

II 

Max. 

Mean 

Min. 

.2 

— 

1.8 

— 

30 

4 

640 

525 

442 

Kept  in  ground. 

.2 

— 

— 

.8 

30 

7 

634 

571 

341 

Kept  in  ground;  26  in.  span. 

.2 

— 

— 

.8 

30 

5 

805 

651 

522 

Kept  in  ground;  30  in.  span. 

.2 

— 

— 

.8 

136 

3 

1249 

993 

730 

Kept  in  ground  all  winter. 

.2 

— 

— 

.8 

30 

14 

913 

689 

444 



T   9 

Of) 

00 

T  19  T 

700 

A&n 

— 

1  .  A 

1.7 

— 

2.75 

.5" 

30 

JJ 

12 

1  i  A  i 

999 

/OJ 

851 

^DU 

677 

(24  hours  in  compressed  air 
(at  7—12  Ibs.  per  sq.  in. 

— 

1.9 

— 

2.6 

30 

50 

924 

850 

590 

(24  hours  in  compressed  air 
(at  12  —  18  Ibs.  per  sq.  in. 

— 

2. 

— 

2.4 

30 

30 

904 

731 

622 

(48  hours  in  compressed  air 
\at  18  —  25  Ibs.  per  sq.  in. 

— 

2. 

— 

2.4 

30 

100 

900 

728 

523 

|  28—30  days   in  compressed 
(air  at  20—25  Ibs.  per  sq.  in. 

2.5 

— 

— 

4. 

3Yrs. 

2 

972 

849 

726 

Buried  in  sand  under  sea  water. 

2.5 

— 

— 

4. 

" 

I 



809 



Buried  in  fresh  earth. 

an  impalpable  powder  to  -J  inch  in  diameter.  It  will  be  seen 
that  the  beams  mixed  with  stone  dust  give  higher  results  than 
those  mixed  with  sand. 

Table  IV.  is  an  abstract  from  the  Report  of  the  Boston  Transit 

TABLE    IV. 


No.  of 

Modulus  of  Rupture  in  Lbs. 

Average 

Remarks 

Beams 

Dimension  - 

per  Sq.  In. 

Days  in 

Tested 

Max'm 

Mean 

Minimum 

Ground 

Ingredients 

(  Cement; 

4.... 

6x6x30  In. 

640 

525 

442 

28 

{  Coarse,  clean  and  sharp  sand; 

(  Gravel. 

7  

5.... 

6x6x26  In. 
6x6x30  In. 

634 
805 

571 
651 

341 
522 

28 
28 

(  Cement; 
j  Coarse,  clean  and  sharp  sand; 
(Trap  rock,  1  in.  to  2%  in. 

f  Cement; 

3-... 

" 

1249 

993 

730 

135 

j  Coarse,  clean  and  sharp  sand; 
(Trap  rock,  1  in.  to  2l/z  in. 

(Cement; 

I4-... 

" 

913 

683 

444 

28 

Coarse,  clean  and  sharp  sand; 

(Trap  rock,  1  in.  to  2^  in. 

33.-.. 

" 

II2I 

777 

460 

<2g      i  (Same  as  above,  but  stone  dust 
i  \  instead  of  sand. 

Commission  for  1901,  and  records  the  results  of  tests  made  on 
concrete  beams  6x6x  about  30  inches  in  length.     The  propor- 


Art.  26.] 


MODULUS  OF  RUPTURE  IN  BENDING. 


155 


tions  of  the  ingredients  of  the  concrete  were  I  Vulcanite  cement, 
2  sand  and  4  broken  stone  of  the  character  as  shown  in  the  col- 
umn headed  "Remarks." 

Table  V.  is  taken  from  results  recorded  by  E.  C.  Clarke  in 
Vol.  XIV.  of  the  Transactions  of  the  American  Society  of  Civil 
Engineers,  and  shows  the  modulus  of  rupture  obtained  for  beams 
10  inches  square  and  about  6  feet  long,  which  were  buried  in  a 

TABLE  V. 


Materials 

Modulus  of  Rupture  in  Lbs.  per  Sq.  In. 

I  Natural  Cement  :  2  Sand  :  *}  Stone  
I«3'7  

67 
176 

1-4-9  

146 

I'6'I  I 

112 

pit  and  tested  when  six  months  old.  The  stone  used  was  screened 
pebbles,  an  inch  or  less  in  diameter.  The  modulus  of  rupture 
as  calculated  includes  the  weight  of  the  beams. 

Table  VI.  is  taken  from  the  Report  of  the  Boston  Transit 
Commission  for  the  year  ending  June  30,  1902,  and  gives  values 
of  the  ultimate  fibre  stress  of  concrete  beams  in  flexure.  The 
cement  was  Vulcanite  Portland.  The  mixing  was  done  by  hand 
and  the  beams  were  kept  the  first  twenty-four  hours  in  air  and 

TABLE   VI.— CONCRETE   BEAMS   6x6x30   IN.,  30    DAYS   OLD. 


Composition  by  Volume 
(Approx.) 

No.  of 
Tests 

Size  of  Stone  Dust 

Ultimate  Fibre  Stress  in  Lbs. 
per  Sq.  In. 

Cement 

Sand 

Stone 
Dust 

Broken 
Stone 

Max. 

Mean 

Min. 

I 

I 

.9 
1.6 
.9 

2 
.9 

.9 

2.4 
2.7 
3 
2.7 

4 
4 
4 
4 

Medium 
Coarse 

947 
846 
773 
862 

848 
784 
711 
806 

760 
704 
656 
759 

then  twenty-nine  days  in  damp  earth.  The  results  are  of  interest 
as  showing  the  comparative  strength  of  mixtures  with  stone  dust 
and  with  sand.  It  will  be  seen  that  those  beams  in  which  the 
stone  dust  replaced  the  sand  were  the  stronger  and  that  in  no 
case  did  the  use  of  stone  dust  weaken  the  mixture. 

Table  VII.  is  taken  from  some  tests  reported  by  T.  S.  Clark, 
in  Engineering  News  of  July  24,  1902,  and  shows  the  relation 


156 


FLEXURAL  PROPERTIES. 


[Ch.  VII. 


between  the  tensile  strength  of  ordinary  tensile  briquettes  and 
the  extreme  fibre  stress  of  small  concrete  beams  1x1x8  inches. 
The  same  cement  and  aggregate  were  used  for  both  kinds  of 
tests  and  subjected  to  exactly  the  same  treatment  at  the  time  of 
mixing.  Each  result  shown  is  an  average  of  from  two  to  twelve 
specimens.  All  the  mixtures  were  kept  twenty-four  hours  in 
air,  and  the  rest  of  the  time  presumably  in  water,  although  it  is 
not  so  specifically  stated.  It  will  be  seen  that  the  ratio  between 
the  ultimate  fibre  stress  in  flexure  as  compared  to  the  tensile 
strength  varies  from  1.32  to  1.66. 

TABLE  VIL 


Compos! 

ion  of  Sp 

;cimen  in 

Parts  of 

Age 

Ult.  Tensile 

Extreme  Fibre 

Ratio  of 

Cement 

Sand 

Stone 

Cinder 

in 

Days 

Strength  in 
Lbs.  per  Sq.  In. 

Stress  in 
Lbs.  per  Sq.  In. 

Tension  to 
Bending 

Neat 

— 

— 

— 

30 

809 

1242 

•  53 

" 

— 

— 

— 

112 

932 

1406 

.50 

2^ 

— 

— 

30 

376 

540 

•  43 

2^ 

— 

— 

60 

482 

634 

.32 

2^ 

— 

— 

112 

493 

679 

.37 

3 

— 

— 

28 

282 

417 

.47 

3 

— 

— 

56 

328 

512 

.56 

I 

2 

*>* 

— 

28 

187 

304 

1.63 

1 

2 

— 

5 

30 

no 

183 

1.66 

*Beams  3x3x30  inches; 

E.  S.  Wheeler  records  in  the  Report  of  the  Chief  of  Engineers, 
U.  S.  Army,  for  1896^  p.  2870,  an  interesting  series  of  tests,  show- 
ing the  relation  between  ultimate  resistances  of  cement  mixtures 
in  tension,  in  bending  and  in  compression ;  the  compression  tests 
will  not  be  considered,  however,  since  crude  apparatus  was  em- 
ployed. 

The  results  from  the  tension  and  bending  experiments  are  per- 
haps comparable,  although  the  actual  tension  values  obtained 
may  be  erroneous,  on  account  of  the  use  of  the  ordinary  tensile 
briquette^  This  statement  applies  similarly  to  the  preceding 
table.  The  transverse  specimens  were  2x2x8  inches,  broken  on 
a  5  i -3-inch  span.  The  specimens  for  the  two  kinds  of  tests 
were  always  prepared  from  the  same  batch  of  mortar ;  each  result 
in  Table  VIII.  is  an  average  of  4  to  10  breakings.  It  will  be 
seen  that  the  ratio  of  the  extreme  fibre  resistance  to  the  tensile 


Art.  27.] 


SHEARING  RESISTANCE  AND  CONCLUSION. 


157 


resistance  averages  about  ij,  having  extreme  values  of  I  1-4  to 
i  9-10.  Experiments  made  with  natural  cements  furnished  sim- 
ilar results. 

Experiments  by  Durand-Claye  (page  149)  and  by  Bauschinger 
(page  27)  have  already  been  noted,  and  their  results  check  the 

TABLE  VIII. 


Mixture 

Tensile  Strength  in  Lbs.  per  Sq.  In. 

Transverse  Strength  in  Lbs.  per  Sq.  In. 

Sand 
to 
Cement 

At  Age  of 

At  Age  of 

1  Day 

7  Days    28  Ds. 

3  Mos. 

1  Year 

1  Day 

7  Days 

28  Ds. 

3  Mos. 

1    Year 

Neat 
1:1 
1:2 
1:3 
1:5 

268 

588         698 
484  i     630 
294  ,  
182  ;     277 

733 
705 
491 
338 
187 

721 

379 
252 

458 

III5 
607 
407 
247 

1237 
915 

397 

1340 
II2I 
764 
541 
286 

1  185 

582 
369 

ratios  obtained  in  Tables  VII.  and  VIII.;  in  conclusion  it  may 
therefore  be  said  that  the  value  of  the  modulus  is  about  ij  times 
the  ultimate  tensile  resistance  of  the  same  material  when  tested 
in  the  standard  briquette  form.  It  seems  doubtful  if  anything 
more  exact  can  at  the  present  time  be  determined. 


Art.  27. — Transverse  Shearing  Resistance  and  Conclusion. 

The  resistance  of  cement  mixtures  to  shearing  stresses  has 
not  been  treated  separately  on  account  of  the  lack  of  experi- 
mental data.  On  page  27  are  given  the  results  of  some  tests  by 
Bauschinger,  and  on  page  95  some  results  obtained  at  Columbia 
University.  It  is  only  possible  to  state  that  the  value  of  the  ulti- 
mate shearing  resistance  varies  between  the  extreme  limits  of  125 
to  375  pounds  per  square  inch.  The  question  of  shear  is  of  the 
greatest  importance,  and  accurate  and  detailed  experiments  of 
the  trasverse  shearing  resistance  of  concrete  would  be  of  great 
value. 

The  elastic  properties  of  reinforced  concrete  beams  have  not 
been  discussed  in  this  work,  except  in  connection  with  results 
having  direct  bearing  on  ordinary  cement  mixtures;  principally 
because,  in  the  opinion  of  the  author,  the  elastic  behavior  of  the 
combination  may  be  deduced  by  analysis,  with  the  aid  of  the 


158  FLEXURAL  PROPERTIES.  [Ch.  VII. 

experimental  values  found  separately  for  the  two  elements.  It 
is  his  opinion  that  the  combination  of  the  two  materials  acts  in 
practice  as  rational  theory  might  require,  although  some  pub- 
lished experiments  ascribe  to  concrete,  when  reinforced,  different 
elastic  properties  than  when  not  reinforced. 


APPENDIX    I. 


REPORT  ON  UNIFORM    TESTS   OF   CEMENT  BY  THE  SPECIAL 

COMMITTEE  OF  THE  AMERICAN  SOCIETY 

OF  CIVIL  ENGINEERS 


T resented  at  the  Annual  Meeting,  January  21,  1903,  and  Amended  at  the  Annual 
Meeting,  January  20,  1904. 


SAMPLING. 

I. — Selection  of  Sample. — The  selection  of  the  sample  for  testing  is  a  detail 
that  must  be  left  to  the  discretion  of  the  engineer ;  the  number  and  the  quan- 
tity to  be  taken  from  each  package  will  depend  largely  on  the  importance  of 
the  work,  the  number  of  tests  to  be  made  and  the  facilities  for  making  them. 

2. — The  sample  shall  be  a  fair  average  of  the  contents  of  the  package;  it  is 
recommended  that,  where  conditions  permit,  one  barrel  in  every  ten  be 
sampled. 

3. — All  samples  should  be  passed  through  a  sieve  having  twenty  meshes 
per  linear  inch,  in  order  to  break  up  lumps  and  remove  foreign  material;  this 
is  also  a  very  effective  method  for  mixing  them  together  in  order  to  obtain  an 
average.  For  determining  the  characteristics  of  a  shipment  of  cement,  the 
individual  samples  may  be  mixed  and  the  average  tested ;  where  time  will 
permit,  however,  it  is  recommended  that  they  be  tested  separately. 

4. — Method  of  Sampling. — Cement  in  barrels  should  be  sampled  through  a 
hole  made  in  the  centre  of  one  of  the  staves,  midway  between  the  heads,  or  in 
the  head,  by  means  of  an  auger  or  a  sampling  iron  similar  to  that  used  by 
sugar  inspectors.  If  in  bags,  it  should  be  taken  from  surface  to  centre. 

CHEMICAL  ANALYSIS. 

5. — Significance. — Chemical  analysis  may  render  valuable  service  in  the 
detection  of  adulteration  of  cement  with  considerable  amounts  of  inert  mate- 
rial, such  as  slag  or  ground  limestone.  It  is  of  use,  also,  in  determining 
whether  certain  constituents,  believed  to  be  harmful  when  in  excess  of  a  cer- 
tain percentage,  as  magnesia  and  sulphuric  anhydride,  are  present  in  inadmissi- 
ble proportions.  While  not  recommending  a  definite  limit  for  these  impurities, 


160 


METHODS  OF  TESTING  CEMENT  BY 


the  Committee  would  suggest  that  the  most  recent  and  reliable  evidence  ap- 
pears to  indicate  that  magnesia  to  the  amount  of  *)%,  and  sulphuric  anhydride 
to  the  amount  of  I.75$>,  may  safely  be  considered  harmless. 

6. — The  determination  of  the  principal  constituents  of  cement — silica, 
alumina,  iron  oxide  and  lime — is  not  conclusive  as  an  indication  of  quality. 
Faulty  character  of  cement  results  more  frequently  from  imperfect  preparation 
of  the  raw  material  or  defective  burning  than  from  incorrect  proportions  of  the 
constituents.  Cement  made  from  very  finely  ground  material,  and  thoroughly 
burned,  may  contain  much  more  lime  than  the  amount  usually  present  and  still 
be  perfectly  sound.  On  the  other  hand,  cements  low  in  lime  may,  on  account 
of  careless  preparation  of  the  raw  material,  be  of  dangerous  character. 
Further,  the  ash  of  the  fuel  used  in  burning  may  so  greatly  modify  the  com- 
position of  the  product  as  largely  to  destroy  the  significance  of  the  results  of 
analysis. 

7. — Method. — As  a  method  to  be  followed  for  the  analysis  of  cement,  that 
proposed  by  the  Committee  on  Uniformity  in  the  Analysis  of  Materials  for  the 
Portland  Cement  Industry,  of  the  New  York  Section  of  the  Society  for  Chem- 
ical Industry,  and  published  in  the  Journal  of  the  Society  for  January  I5th, 
1902,  is  recommended. 

SPECIFIC  GRAVITY. 

8. — Significance. — The  specific  gravity  of  cement  is  lowered  by  underburn- 
ing,  adulteration  and  hydration,  but  the  adulteration  must  be  in  considerable 

quantity  to  affect  the  results  appreci- 
ably. 

9. — Inasmuch  as  the  differences  in 
specific  gravity  are  usually  very 
small,  great  care  must  be  exercised 
in  making  the  determination. 

10. — When  properly  made,  this  test 
affords  a  quick  check  for  under- 
burning  or  adulteration. 

II. — Apparatus  and  Method. — The 
determination  of  specific  gravity  is 
most  conveniently  made  with  Le 
Chatelier's  apparatus.  This  consists 
of  a  flask  (D),  Fig.  I,  of  120  cu.  cm. 
(7.32  cu.  ins.)  capacity,  the  neck  of 
which  is  about  20  cm.  (7.87  ins.)  long; 
in  the  middle  of  this  neck  is  a  bulb 
(C),  above  and  below  which  are  two  marks  (F)  and  (£);  the  volume  between 
these  marks  is  20  cu.  cm.  (1.22  cu.  ins.).  The  neck  has  a  diameter  of  about  9 
mm.  (0.35  in.),  and  is  graduated  into  tenths  of  cubic  centimeters  above  the  bulb. 
12. — Benzine  (62°  Baume  naphtha),  or  kerosene  free  from  water,  should 
be  used  in  making  the  determination. 

13. — The  specific  gravity  can  be  determined  in  two  ways. 


Le  Chatelier's  Specific  Gravity  Apparatus. 
FIG.  1. 


77ZE  AMERICAN  SOCIETY  OF  CIVIL  ENGINEERS.  1 6 1 

(I)  The  flask  is  filled  with  either  of  these  liquids  to  the  lower  mark  (E  , 
and  64  gr.  (2.25  oz.)  of  powder,  previously  dried  at  100°  Cent.  (212°  Fahr. ) 
and  cooled  to  the  temperature  of  this  liquid,  is  gradually  introduced  through 
the  funnel  (B)  [the  stem  of  which  extends  into  the  flask  to  the  top  of  the 
bulb  (C)],  until  the  upper  mark  (F)  is  reached.  The  difference  in  weight 
between  the  cement  remaining  and  the  original  quantity  (64  gr. )  is  the  weight 
which  has  displaced  20  c\i.  cm. 

14- — (2)  The  whole  quantity  of  the  powder  is  introduced  and  the  level  of 
the  liquid  rises  to  some  division  of  the  graduated  neck.  This  reading  plus 
20  cu.  cm.  is  the  volume  displaced  by  64  gr.  of  the  powder. 

15. — The  specific  gravity  is  then  obtained  from  the  formula: 

,-.        ...      „  Weight  of  Cement 

Specific  Gravity— — — 

Displaced  Volume. 

16. — The  flask,  during  the  operation,  is  kept  immersed  in  water  in  a  jar 
(A},  in  order  to  avoid  variations  in  the  temperature  of  the  liquid.  The 
results  should  agree  within  0.01. 

17. — A  convenient  method  for  cleaning  the  apparatus  is  as  follows:  The 
flask  is  inverted  over  a  large  vessel,  preferably  a  glass  jar,  and  shaken  ver- 
tically until  the  liquid  starts  to  flow  freely  ;  it  is  then  held  still  in  a  vertical 
position  until  empty  ;  the  remaining  traces  of  cement  can  be  removed  in  a 
similar  manner  by  pouring  into  the  flask  a  small  quantity  of  clean  liquid  and 
repeating  the  operation. 

18. — More  accurate  determinations  may  be  made  with  the  picnometer. 

FINENESS. 

19. — Significance. — It  is  generally  accepted  that  the  coarser  particles  in 
cement  are  practically  inert,  and  it  is  only  the  extremely  fine  powder  that 
possesses  adhesive  or  cementing  qualities.  The  more  finely  cement  is  pul- 
verized, all  other  conditions  being  the  same,  the  more  sand  it  will  carry  and 
produce  a  mortar  of  a  given  strength. 

20. — The  degree  of  final  pulverization  which  the  cement  receives  at  the 
place  of  manufacture  is  ascertained  by  measuring  the  residue  retained  on 
certain  sieves.  Those  known  as  the  No.  100  and  No.  200  sieves  are  recom- 
mended for  this  purpose. 

21. — Apparatus. — The  sieves  should  be  circular,  about  20  cm.  (7.87  ins. ) 
in  diameter,  6  cm.  (2.36  ins.)  high,  and  provided  with  a  pan,  5  cm.  (1.97  ins. ) 
deep,  and  a  cover. 

22. — The  wire  cloth  should  be  woven  (not  twilled)  from  brass  wire  having 
the  following  diameters  : 

No.  100,  0.0045  in.;   No.  200,  0.0024  in. 

23. — This  cloth  should  be  mounted  on  the  frames  without  distortion;  the 
mesh  should  be  regular  in  spacing  and  be  within  the  following  limits: 
No.  100,  96  to  100  meshes  to  the  linear  inch. 
No.  200,  188  to  200     " 


162 


METHODS  OF  TESTING  CEMENT  BY 


24. — Fifty  grams  (l.76oz.)  or  100  gr.  (3-52  oz.)  should  be  used  for  the 
test,  and  dried  at  a  temperature  of  100°  Cent.  (212°  Fahr. )  prior  to  sieving. 

25. — Method. — The  Committee,  after  careful  investigation,  has  reached  the 
conclusion  that  mechanical  sieving  is  not  as  practicable  or  efficient  as  hand 
work,  and,  therefore,  recommends  the  following  method: 

26. — The  thoroughly  dried  and  coarsely  screened  sample  is  weighed  and 
placed  on  the  No.  200  sieve,  which,  with  pan  and  cover  attached,  is  held  in 
one  hand  in  a  slightly  inclined  position,  and  moved  forward  and  backward,  at 
the  same  time  striking  the  side  gently  with  the  palm  of  the  other  hand,  at  the 
rat3  of  about  200  strokes  per  minute.  The  operation  is  continued  until  not 
more  than  one-tenth  of  \%  passes  through  after  one  minute  of  continuous 
sieving.  The  residue  is  weighed,  then  placed  on  the  No.  100  sieve  and  the 
operation  repeated.  The  work  may  be  expedited  by  placing  in  the  sieve  a 
small  quantity  of  large  shot.  The  results  should  be  reported  to  the  nearest 
tenth  of  I  per  cent 

NORMAL  CONSISTENCY. 

27. — Significance. — The  use  of  a  proper  percentage  of  water  in  making  the 
pastes*  from  which  pats,  tests  of  setting  and  briquettes  are  made,  is  exceed- 
ingly important,  and  affects  vitally  the  results  obtained. 

28. — The  determination  consists  in  measuring  the  amount  of  water  required 
to  reduce  the  cement  to  a  given  state  of  plasticity,  or  to  what  is  usually  desig- 
nated the  normal  consistency. 

29. — Various  methods  have  been  proposed  for  making  this  determination, 
none  of  which  has  been  found  entirely  satisfactory.  The  Committee  recom- 
mends the  following  : 

30.— Method.     Vicat  Needle  Apparatus.—  This  consists  of  a  frame  (/Q,  Fig. 

2,  bearing  a  movable  rod  (/.),  with  the 
cap  (A]  at  one  end,  and  at  the  other 
end  the  cylinder  (B),  I  cm.  (0.39  in.)  in 
diameter,  the  cap,  rod  and  cylinder  weigh- 
ing 300  gr.  (10.58  oz.).  The  rod,  which 
can  be  held  in  any  desired  position  by  a 
screw  (F),  carries  an  indicator,  which 
moves  over  a  scale  (graduated  to  centi- 
meters) attached  to  the  frame  (K).  The 
paste  is  held  by  a  conical,  hard-rubber 
ring  (/),  7  cm.  (2.76  ins.)  in  diameter  at 
the  base,  4  cm.  (1.57  ins.)  high,  resting  on 
a  glass  plate  (/),  about  10  cm.  (3.94  ins.i 
square. 

31.  —  In  making  the  determination,  the  same  quantity  of  cement  as  will  be 
subsequently  used  for  each  batch  in  making  the  briquettes  (but  not  less  than 


and 


*The  term  "paste"  is  used  in  this  report  to  designate  a  mixture  of  cement  and   water, 
the  word  "mortar"  a  mixture  of  cement,  sand  and  water. 


THE  AMERICAN  SOCIETY  OF  CIVIL  ENGINEERS.  1 63 

500  grammes)  is  kneaded  into  a  paste,  as  described  in  Paragraph  58,  and 
quickly  formed  into  a  ball  with  the  hands,  completing  the  operation  by  tossing 
it  six  times  from  one  hand  to  the  other,  maintained  6  ins.  apart;  the  ball  is 
then  pressed  into  the  rubber  ring,  through  the  larger  opening,  smoothed  off 
and  placed  on  a  glass  plate  (on  its  large  end)  and  the  smaller  end  smoothed 
off  with  a  trowel;  the  paste,  confined  in  the  ring,  resting  on  the  plate,  is 
placed  under  the  rod  bearing  the  cylinder,  which  is  brought  in  contact  with 
the  surface  and  quickly  released. 

32. — The  paste  is  of  normal  consistency  when  the  cylinder  penetrates  to 
a  point  in  the  mass  10  mm.  (0.39  in.)  below  the  top  of  the  ring.  Great  care 
must  be  taken  to  fill  the  ring  exactly  to  the  top. 

33.—  The  trial  plates  are  made  with  varying  percentages  of  water  until 
the  correct  consistency  is  obtained. 

34- — The  Committee  has  recommended,  as  normal,  a  paste  the  consistency 
of  which  is  rather  wet,  because  it  believes  that  variations  in  the  amount  of 
compression  to  which  the  briquette  is  subjected  in  moulding  are  likely  to  be 
less  with  such  a  paste. 

35- — Having  determined  in  this  manner  the  proper  percentage  of  water  re- 
quired to  produce  a  neat  paste  of  normal  consistency,  the  proper  percentage 
required  for  the  sand  mortars  is  obtained  from  an  empirical  formula. 

36. —  The  Committee  hopes  to  devise  such  a  formula.  The  subject  proves 
to  be  a  very  difficult  one,  and,  although  the  Committee  has  given  it  much  study, 
it  is  not  yet  prepared  to  make  a  definite  recommendation. 

TIME  OF  SETTING. 

37. — Significance. — The  object  of  this  test  is  to  determine  the  time  which 
elapses  from  the  moment  water  is  added  until  the  paste  ceases  to  be  fluid  and 
plastic  (called  the  "initial  set"),  and  also  the  time  required  for  it  to  acquire  a 
certain  degree  of  hardness  (called  the  "final"  or  "hard  set").  The  former 
of  these  is  the  more  important,  since,  with  the  commencement  of  setting,  the 
process  of  crystallization  or  hardening  is  said  to  begin.  As  a  disturbance  of 
this  process  may  produce  a  loss  of  strength,  it  is  desirable  to  complete  the 
operation  of  mixing  and  moulding  or  incorporating  the  mortar  into  the  work 
before  the  cement  begins  to  set. 

38. — It  is  usual  to  measure  arbitrarily  the  beginning  and  end  of  the  setting 
by  the  penetration  of  weighted  wires  of  given  diameters. 

39. — Method. — For  this  purpose  the  Vicat  Needle,  which  has  already  been 
described  in  Paragraph  30,  should  be  used. 

40. — In  making  the  test,  a  paste  of  normal  consistency  is  moulded  and 
placed  under  the  rod  (L),  Fig.  2,  as  described  in  Paragraph  31;  this  rod,  bear- 
ing the  cap  (D)  at  one  end  and  the  needle  (//),  I  mm.  (0.039  in.)  in  diameter, 
at  the  other,  weighing  300  gr.  (10.58  oz.).  The  needle  is  then  carefully  brought 
in  contact  with  the  surface  of  the  paste  and  quickly  released. 

41. — The  setting  is  said  to  have  commenced  when  the  needle  ceases  to  pass 
a  point  5  mm.  (0.20  in.)  above  the  upper  surface  of  the  glass  plate,  and  is 


164 


METHODS  OF  TESTING  CEMENT  BY 


.  ^, 

] 

Details 

I 

for  Briquette. 
'IG.  3. 

said  to  have   terminated   the   moment  the  needle  does  not  sink  visibly  into  the 

mass. 

42. — The  test  pieces  should  be  stored  in  moist  air  during  the  test;  this  is 
accomplished  by  placing  them  on  a  rack  over 
water  contained  in  a  pan  an«l  covered  with 
a  damp  cloth,  the  cloth  to  be  kept  away  from 
them  by  means  of  a  wire  screen;  or  they  may 
be  stored  in  a  moist  box  or  closet. 

43. — Care  should  be  taken  to  keep  the 
needle  clean,  as  the  collection  of  cement  on 
the  sides  of  the  needle  retards  the  penetra- 
tion, while  cement  on  the  point  reduces  the 
area  and  tends  to  increase  the  penetration. 

44- — The  determination  of  the  time  of  set- 
ting is  only  approximate,  being  materially 
affected  by  the  temperature  of  the  mixing 
water,  the  temperature  and  humidity  of  the  air 
during  the  test,  the  percentage  of  water  used, 
and  the  amount  of  moulding  the  paste  re- 
ceives. 

STANDARD    SAND. 

45« — The  Committee  recognizes  the  grave  objections  to  the  standard  quartz 
now  generally  used,  especially  on  account  of  its  high  percentage  of  voids,  the 
difficulty  of  compacting  in  the  moulds,  and  its  lack  of  uniformity;  it  has 
spent  much  time  in  investigating  the  various  natural  sands  which  appeared  to 
be  available  and  suitable  for  use. 

46. — For  the  present,  the  Committee  recommends  the  natural  sand  from 
Ottawa,  111.,  screened  to  pass  a  sieve  having  20  meshes  per  linear  inch  and 
retained  on  a  sieve  having  30  meshes  per  linear  inch ;  the  wires  to  have  diam- 
eters of  0.0165  and  O.OII2  in.,  respectively,  i.  e.,  half  the  width  of  the  opening 
in  each  case.  Sand  having  passed  the  No.  20  sieve  shall  be  considered  stand- 
ard when  not  more  than  one  per  cent,  passes  a  No.  30  sieve,  after  one  minute 
continuous  sifting  of  a  500-gram  sample. 

47. — The  Sandusky  Portland  Cement  Company,  of  Sandusky,  Ohio,  has 
agreed  to  undertake  the  preparation  of  this  sand,  and  to  furnish  it  at  a  price 
only  sufficient  to  cover  the  actual  cost  of  preparation. 

.      FORM    OF    BRIQUETTE. 

48.  — While  the  form  of  the  briquette  recommended  by  a  former  Com- 
mittee of  the  Society  is  not  wholly  satisfactory,  this  Committee  is  not  pre- 
pared to  suggest  any  change,  other  than  rounding  off  the  corners  by  curves  of 

X-in.  radius.  Fig.  3. 

MOULDS. 

49- — The  moulds  should  be  made  of  brass,   bronze  or  some  equally   non- 


THE  AMERICAN  SOCIETY  OF  CIVIL  ENGINEERS.  1 65 

corrodible  material  having  sufficient  metal  in  the  sides  to  prevent  spreading 
during  moulding. 

50. — Gang  moulds,  which  permit 
moulding  a  number  of  briquettes  at 
one  time,  are  preferred  by  many  to 
single  moulds;  since  the  greater  Details  for^Gang  Mould, 

quantity  of  mortar  that  can  be  mixed 

tends  to  produce  greater  uniformity  in  the  results.     The  type  shown  in  Fig.  4 
is  recommended. 

51, — The  moulds  should  be  wiped  with  an  oily  cloth  beiore  using. 

MIXING. 

52. — All  proportions  should  be  stated  by  weight;  the  quantity  of  water  to 
be  used  should  be  stated  as  a  percentage  of  the  dry  material. 

53. — The  metric  system  is  recommended  because  of  the  convenient  relation 
of  the  gram  and  the  cubic  centimeter. 

54. — The  temperature  of  the  room  and  the  mixing  water  should  be  as  near 
21°  Cent.  (70°  Fahr.)  as  «t  is  practicable  to  maintain  it. 

55- — The  sand  and  cement  should  be  thoroughly  mixed  dry.  The  mixing 
should  be  done  on  some  non-absorbing  surface,  preferably  plate  glass.  If  the 
mixing  must  be  done  on  an  absorbing  surface  it  should  be  thoroughly  dampened 
prior  to  use. 

56. — The  quantity  of  material  to  be  mixed  at  one  time  depends  on  the 
number  of  test  pieces  to  be  made;  about  1,000  gr.  (35-28  oz.)  makes  a  conven- 
ient quantity  to  mix,  especially  by  hand  methods. 

57. — The  Committee,  after  investigation  of  the  various  mechanical  mixing 
machines,  has  decided  not  to  recommend  any  machine  that  has  thus  far  been 
devised,  for  the  following  reasons: 

(I)  The  tendency  of  most  cement  is  to  "ball  up"  in  the  machine,  thereby 
preventing  the  working  of  it  into  a  homogeneous  paste;  (2)  there  are  no  means 
of  ascertaining  when  the  mixing  is  complete  without  stopping  the  machine,  and 
(3)  the  difficulty  of  keeping  the  machine  clean. 

53. — Method. — The  material  is  weighed  and  placed  on  the  mixing  table, 
and  a  crater  formed  in  the  centre,  into  which  the  proper  percentage  of  clean 
water  is  poured;  the  material  on  the  outer  edge  is  turned  into  the  crater  by  the 
aid  of  a  trowel.  As  soon  as  the  water  has  been  absorbed,  which  should  not 
require  more  than  one  minute,  the  operation  is  completed  by  vigorously 
kneading  with  the  hands  for  an  additional  IJ^  minutes,  the  process  being 
similar  to  that  used  in  kneading  dough.  A  sand-glass  affords  a  convenient 
guide  for  the  time  of  kneading.  During  the  operation  of  mixing  the  hands 
should  be  protected  by  gloves,  preferably  of  rubber. 

MOULDING. 

59. — Having  worked  the  paste  or  mortar  to  the  proper  consistency,  it  is  at 
once  placed  in  the  moulds  by  hand. 

60.  —  The  Committee  has  been  unable  to  secure  satisfactory  results  with  the 


166 


METHODS  OF  TESTING  CEMENT  BY 


present  moulding  machines;  the  operation  of  machine  moulding  is  very  slow, 
and  the  present  types  permit  of  moulding  but  one  briquette  at  a  time,  and  are 
not  practicable  with  the  pastes  or  mortars  herein  recommended. 

61. — Method. — The  moulds  should  be  filled  at  once,  the  material  pressed  in 
firmly  with  the  fingers  and  smoothed  off  with  a  trowel  without  ramming;  the 
material  should  be  heaped  up  on  the  upper  surface  of  the  mould,  and,  in 
smoothing  off,  the  trowel  should  be  drawn  over  the  mould  in  such  a  manner  as 
to  exert  a  moderate  pressure  on  the  excess  material.  The  mould  should  be 
turned  over  and  the  operation  repeated. 

62. — A  check  upon  the  uniformity  of  the  mixing  and  moulding  is  afforded 
by  weighing  the  briquettes  just  prior  to  immersion,  or  upon  removal  from  the 
moist  closet.  Briquettes  which  vary  in  weight  more  than  3  per  cent,  from  the 
average  should  not  be  tested. 

STORAGE  OF  THE  TEST  PIECES. 

63. — During  the  first  24  hours  after  moulding  the  test  pieces  should  be  kept 
in  moist  air  to  prevent  them  from  drying  out. 

64. — A  moist  closet  or  chamber  is  so  easily  devised  that  the  use  of  the  damp 
cloth  should  be  abandoned  if  possible.  Covering  the  test 
pieces  with  a  damp  cloth  is  objectionable,  as  commonly 
used,  because  the  cloth  may  dry  out  unequally,  and,  in 
consequence,  all  the  test  pieces  are  not  maintained  under 
the  same  condition.  Where  a  moist  closet  is  not  avail- 
able, a  cloth  may  be  used  and  kept  uniformly  wet  by 
immersing  the  ends  in  water.  It  should  be  kept  from 
direct  contact  with  ths  test  pieces  by  means  of  a  wire 
screen  or  some  similar  arrangement. 

65. — A  moist  closet  consists  of  a  soapstone  or  slate 
box,  or  a  metal-lined  wooden  box — the  metal  lining  being 
covered  with  felt  and  this  felt  kept  wet.  The  bottom  of 
the  box  is  so  constructed  as  to  hold  water,  and  the  sides 
are  provided  with  cleats  for  holding  glass  shelves  on  which 
to  place  the  briquettes.  Care  should  be  taken  to  keep  the 
air  in  the  closet  uniformly  moist. 

66. — After  24  hours  in  moist  air  the  test  pieces  for 
longer  periods  of  time  should  be  immersed  in  water  main- 
tained as  near  21°  Cent.  (70°  Fahr. )  as  practicable;  they  may  be  stored  in. 
tanks  or  pans,  which  should  be  of  non-corrodible  material. 

TENSILE  STRENGTH. 

67. — The  tests  may  be  made  on  any  standard  machine.  A  solid  metal 
clip,  as  shown  in  Fig.  5>  is  recommended.  This  clip  is  to  be  used  without 
cushioning  at  the  points  of  contact  with  the  test  specimen.  The  bearing  at 
each  point  of  contact  should  be  }i  in.  wide,  and  the  distance  between  the  cen- 
tre of  contact  on  the  same  clip  should  be  \%  ins. 


Form  of  Clip. 
FIG.  5. 


THE  AMERICAN  SOCIETY  OF  CIVIL  ENGINEERS.  167 

68. — Test  pieces  should  be  broken  as  soon  as  they  are  removed  from  the 
water.  Care  should  be  observed  in  centring  the  briquettes  in  the  testing  ma- 
chine, as  cross-strains,  produced  by  improper  centring,  tend  to  lower  the  break- 
ing strength.  The  load  should  not  be  applied  too  suddenly,  as  it  may  produce 
vibration,  the  shock  from  which  often  breaks  the  briquette  before  the  ultimate 
strength  is  reached.  Care  must  be  taken  that  the  clips  and  the  sides  of  the 
briquette  be  clean  and  free  from  grains  of  sand  or  dirt,  which  would  prevent  a 
good  bearing.  The  load  should  be  applied  at  the  rate  of  600  Ibs.  per  minute. 
The  average  of  the  briquettes  of  each  sample  tested  should  be  taken  as  the 
test,  excluding  any  results  which  are  manifestly  faulty. 

CONSTANCY  OF  VOLUME. 

69. — Significance. — The  object  is  to  develop  those  qualities  which  tend  to 
destroy  the  strength  and  durability  of  a  cement.  As  it  is  highly  essential  to  de- 
termine such  qualities  at  once,  tests  of  this  character  are  for  the  most  part 
made  in  a  very  short  time,  and  are  known,  therefore,  as  accelerated  tests. 
Failure  is  revealed  by  cracking,  checking,  swelling  or  disintegration,  or  all  of 
these  phenomena.  A  cement  which  remains  perfectly  sound  is  said  to  be  of 
constant  volume. 

70. — Methods. — Tests  for  constancy  of  volume  are  divided  into  two  classes: 
(I)  normal  tests,  or  those  made  in  either  air  or  water  maintained  at  about  21° 
Cent.  (70°  Fahr.),  and  (2)  accelerated  tests,  or  those  made  in  air,  steam  or 
water  at  a  temperature  of  45°  Cent.  (115°  Fahr.)  and  upward.  The  test  pieces 
should  be  allowed  to  remain  24  hours  in  moist  air  before  immersion  in  water 
or  steam  or  preservation  in  air. 

71. — For  these  tests,  pats,  about  7^  cm.  (2.95  ins.)  in  diameter,  1%  cm. 
(0.49  in.)  thick  at  the  centre,  and  tapering  to  a  thin  edge,  should  be  made,  upon 
a  clean  glass  plate  [about  10  cm.  (3.94  ins.)  square],  from  cement  paste  of 
normal  consistency. 

72. — Normal  Test. — A  pat  is  immersed  in  water  maintained  as  near  21° 
Cent.  (70°  Fahr.)  as  possible  for  28  days,  and  observed  at  intervals;  the  pat 
should  remain  firm  and  hard  and  show  no  signs  of  cracking,  distortion  or 
disintegration.  A  similar  pat  is  maintained  in  air  at  ordinary  temperature,  and 
observed  at  intervals. 

73- — Accelerated  Test. — A  pat  is  exposed  in  any  convenient  way  in  an 
atmosphere  of  steam,  above  boiling  water,  in  a  loosely  closed  vessel,  for  three 
hours. 

74. — To  pass  these  tests  satisfactorily  the  pats  should  remain  firm  and 
hard,  and  show  no  signs  of  cracking,  distortion  or  disintegration. 

75. — Should  the  pat  leave  the  plate,  distortion  may  be  detected  best  with  a 
straight-edge  applied  to  the  surface  which  was  in  contact  with  the  plate. 

76. — In  the  present  state  of  our  knowledge  it  cannot  be  said  that  cement 
should  necessarily  be  condemned  simply  for  failure  to  pass  the  accelerated 


168 


METHODS  OF  TESTING  CEMENT. 


tests;  nor  can  a  cement  be  considered  entirely  satisfactory  simply  because  it 
has  passed  these  tests. 

Submitted  on  behalf  of  the  Committee. 

GEORGE  S.  WEBSTER, 

Chairman. 
RICHARD  L.  HUMPHREY, 

Secretary. 
Committee. 

GEORGE  S.  WEBSTER, 
RICHARD  L.  HUMPHREY, 
GEORGE  F.  SWAIN, 
ALFRED  NOBLE, 
LOUIS  C.  SABIN, 
S.  B.  NEWBERRY, 
CLIFFORD  RICHARDSON, 
W.  B.  W,  HOWE, 
F.  H.  LEWIS. 


APPENDIX    II. 


CONSTITUTION    OF    PORTLAND    CEMENT. 

Clifford  Richardson,  in  a  paper  read  before  the  Association  of  Portland 
Cement  Manufacturers,  at  Atlantic  City,  June  15,  1904,  has  advanced  consid- 
erably the  knowledge  concerning  the  constitution  of  Portland  cements. 

Le  Chatelier  and,  independently  of  him,  Tb'rnebohm  have  found,  as  a  result 
of  studies  by  microscopic  methods,  that  clinker  consists  of  four  constituents — 
alit,  belit,  celit  and  felit,  whose  sections  have  distinct  optical  properties,  and 
of  a  fifth  amorphous  isotropic  mass  which  has  no  action  upon  polarized  light. 
Alit  and  celit  are  the  principal  constituents  of  clinker. 

Richardson,  from  his  own  work,  concludes  that  clinker  is  a  solid  solu- 
tion of  silicates  and  aluminates;  alit  being  a  solution  of  tricalcic  aluminate 
(Al.2O33.CaO),  in  tricalcic  silicate  (SiO2  3CaO),  and  celit  a  solution  of  dicalcic 
aluminate  (Al2O3.2CaO)  in  dicalcic  silicate  (SiO2.2CaO).  The  presence  of 
iron,  magnesia,  etc.,  exerts  no  essential  influence,  although  probably  adding  to 
the  complexity  of  the  solid  solutions  present. 

The  formation  of  clinker  from  pure  chemicals  at  a  temperature  below  fusion 
is  probably  due  to  diffusion  and  subsequent  interaction;  this  has  been  shown 
for  other  solid  substances,  as,  for  example,  in  the  production  of  barium  sulphate 
and  sodium  carbonate  from  a  finely  pulverized  mixture  of  sodium  sulphate  and 
barium  carbonate  maintained  in  continued  close  contact. 

Concerning,  therefore,  the  manufacture  of  cements  Richardson  states,  from 
the  viewpoint  of  the  diffusion  of  solid  substances,  as  shown  by  the  above 
example,  that  finer  grinding  of  the  raw  mixture  would  make  possible  the  use 
of  lower  temperatures  in  burning,  and  that  therefore  the  relative  costs  of  fuel 
and  fineness  of  grinding  at  any  given  locality  will  determine,  from  an  econ- 
omic standpoint,  the  fineness  to  which  the  raw  materials  should  be  ground. 

Richardson's  work,  while  not  settling  the  constitution  of  cement  mixtures, 
is  of  the  greatest  importance,  not  only  for  what  it  has  already  accomplished, 
but  also  for  the  possibilities  and  methods  of  investigation  it  suggests;  and  it 
may  reasonably  be  expected  that  in  a  relatively  short  time  the  question  of  the 
constitution  of  cements  will  be  made  as  clear  as  is  that  of  the  different. forms 
of  iron.  His  work  corroborates  the  conclusion,  previously  stated  in  Chapter  I., 
that  a  simple  chemical  analysis  of  the  constituents  present  in  a  cement  can,  as 
yet,  furnish  little  evidence  of  its  quality  or  as  to  its  fitness  for  use. 


INDEX. 


PAGE 

Accelerated   tests 39,  167 

Adhesion  of  iron  in  concrete 61-66 

Aggregate  ;   character  of,  effect  on  strength 30-39 

Analyses  of  natural  cement 6-8 

Analyses  of  Portland  cement 3-6 

Beams,  concrete .' 142-158 

Bending  (see  flexure). 

Blowing  of  cements 3,  39 

Briquette,  form  of,  for  tensile  testing 164 

Chemical  analyses 3-8,  159 

Cinder  concretes  in  compression 83,  III,    113 

Cinder  concretes  in  tension 78 

Clay,  effect  of,  on  strength 34-39 

Coefficient  of  elasticity,  explained 70-75 

Coefficient  of  elasticity,   in  compression 99-121 

Coefficient  of  elasticity,  in  flexure 144- 149 

Coefficient  of  elasticity,  in  tension 75-98 

Coefficient  of  linear  thermal  expansion 43-45 

Cold,  effect  of,  on  cement  mixtures 55-61 

Commercial  physical  tests,  discussed 9-39 

Commercial  physical  tests,  of  American  Soc.  of  Civ.  Eng 159-168 

Compression,  author's  conclusions  on 1 32- 141 

Compression,  coefficient  of  elasticity 91,  95,  96,  99-121 

Compression,  coefficient  of  elasticity  compared  to  tensile  coefficient, 

83,  88,   141 

Compression,  ultimate  resistance  to 83,  99-141 

Compression,  ultimate  resistance  to,  hardening  in  sea  water 47 

Compression,  ultimate  resistance  to,  effect  of  size  of  specimen 106 

Compression,  ultimate  resistance  to,  use  of  cushions 108 

Compression;  ultimate  resistance  compared  to  tensile  resistance 26-29 

Consistency,  normal 162 

Constancy  of  volume,  test  of 39,  167 

Constitution  of  Portland  cement 1-8,  169 

Contraction  of  cements  on  hardening. 40-43 

Crushing  (see  compression). 


172  INDEX. 

PAGE 

Curves,  stress-strain,    explained 70-75 

Curves,  stress-strain,  for  compression. .    88-95,  103,  107-109,  112,  II6-II8,  120 
Curves,  stress-strain,  for  tension 81,  88-95 

Definition  of  a  cement j 

Disintegration  of  cement  mixtures,  in  sea  waters 45-47,  52 

Dry  concrete  against  wet  (see  wet  . 

Effect  of  freezing 55-61 

Elastic  limit,  explained 71 

Expansion,  due  to  temperature  changes .  43-45 

Expansion  of  cements  during  setting 40-43 

Fatigue  of  cement  mixtures 66-69 

Fibre  stress,  extreme,  in  concrete  beams 146-158 

Final  setting  of  cements \T>>  153 

Fineness  test 1 1-13,  i£l 

Fineness  of  sands,  effect  of,  in  tensile  strength 30-39 

Flexural  coefficient  of  elasticity 144 

Flexural  properties  of  cement  mixtures 142-158 

Freezing,  effect  of 55-61 

High  temperatures 132 

Hot  water  test 39 

Impervious  concrete 51-55 

Initial  setting 13^  153 

Loam  in  sands 34-39 

Magnesia,  limit  of,  in  cement 3 

Manufacture  of  cement 9 

Mica,  effect  of 1 29 

Mixing  cement  for  testing 165 

Modulus  of  elasticity  (see  coefficient  of  elasticity). 

Modulus  of  rupture  in  flexure 146-158 

Modulus  of  rupture,  ratio  to  tensile  stress 157 

Moulds,  for  tensile  tests , 164 

Natural  cement,  definition I 

Permeability  of  cement  mixtures 51-55 

Plaster  of  paris,  action  in  delaying  set 14 

Plaster  of  paris,  effect  on  strength  when  setting  is  retarded 18 

Plaster  of  paris,  effect  on  variation  of  volume  during  setting 41 

Plaster  of  paris,  limit  of,  in  cements 3 

Plasticity  of  concretes  (see  wet). 

Porosity 51-55,  140 

Portland  cement,  definition I 

Pozzalana,  addition  of,  to  cements 45-51 


INDEX.  173 

PAGE 

Rate  of  application  of  stress  to  concrete 67 

Ratio  of  modulus  of  rupture  to  tensile  resistance 157 

Reinforced  concrete,  tests  in  tension 76 

Reinforced  concrete,  author's  opinion  on 157 

Repeated  applications  of  stress 66,  100 

Repeated  applications  of  stress,  effect  on  coefficient  of  elasticity 73 

Resistance  to  stress  (see  tension,  compression,  flexure,  shear). 

Retarding  setting  of  cements 57 

Rods,  adhesion  of  iron,  in  concrete 61-66 

Salt,  effect  of,   in  gauging 50,  56 

Sampling  cement  for  purposes  of  test 159 

Sands,  variation  of,  in  tensile  tests 30-39 

Sands,  washed  vs.  unwashed 35-39 

Screenings  (rock)  in  place  of  sand 30-39,  155 

Sea  water,  action  of 45-5 1 

Sea  water,  strength  in 47-5 1 

Setting,  effect  of  plaster  of  paris  on 14 

Setting,  tests  for  time  of 13-19,  163 

Setting,  theories  of I,    169 

Setting  under  water 130 

Shear,  adhesive  (see  adhesion). 

Shear,  transverse,  ultimate  resistance  to 27,  95,  148,  157 

Shrinkage  during  setting 40-43 

Sieves,  size  of 12,  161 

Solution,  solid,  cement  as  a 169 

Specific  gravity  tests 10,  160 

Standard  sand  for  tensile  tests 164 

Storage  of  test  pieces 1 66 

Straight  line  formula  for  coefficient  of  elasticity 132-1^8 

Straight  line  formula  for  ultimate  resistance 1 38- 141 

Strength,  gauged  with  salt  water , 50 

Strength  in  sea  water 47 

Strength  (see  tension),  compression,  flexure,  shear. 
Stress-strain  curves  (see  curves). 

Temperature  changes  during  setting 18 

Temperature,  effect  of,   on  setting 16 

Temperature,  effect  of  high,  on  ultimate  resistance 132 

Tensile  properties,  coefficient  of  elasticity  and  ultimate  resistance 75-98 

Tensile  properties,  conclusions  as  to 97 

Tensile  strength,  effect  on  of  variations  of  sands 30-39 

Tensile  strength,  tests  of,  on  standard  briquettes 19-26,  166 

Tensile  strength,  tests  of,  hardening  in  sea  water 47 

Tensile  strength,  ratio  of,  to  compressive  strength 26-29 

Tensile  strength,  variations  in  methods  of  determining 29 


174  INDEX. 

PAGE 

Tests,  commercial 9 

Theory  of  flexure,  applied  to  concrete 142 

Thermal  expansion,  coefficient  of 43-45 

Time  of  setting  (see  setting). 

Twisted  rods  vs.  plain  rods,  adhesion 61 

U  Itimate  resistance  in  compression 99-141 

Ultimate  resistance  in  tension 75-98 

Ultimate  resistance  in  flexure 146-158 

Ultimate  resistance  in  transverse  shear 27,  157 

Variation  in  volume,  during  setting 40-43 

Variation  in  volume,  due  to  temperature 43-45 

Variation  of  stone  in  concrete,  effect  on  ultimate  resistance 129 

Vicat  needle 162 

Water,  hardening  under 130 

Wet  vs.  dry  concretes 82,  121,  130 


AUTHORS'     INDEX. 


( Italics  Indicate  Journals. ) 


Adie 44 

American  Society  of  Civil  Engineers, 
Transactions  of....  6,  9,  12,  13,  21,  23,  35, 
40,  42,  50,  53,  66, 118,  123,  144, 152, 155, 159 
American  Society  for  Testing  Materi- 
als, Proceedings  of. .  32,  51,  59,  63,  83, 119 
Annales  des  Fonts  et  Chausees. ...  20,  31, 33, 
43,  45,  52,  65,  66,  75,  148 
Arsenal  Reports;  see  Watertown. 

Assoc.  Eng.  Societies,  Journ.  of 24  78 

Austrian  Society  of  Civil  Engineers. . . 

92,  96,  136 

Bach,C 71,99-105,133,  138 

Baker,  B 103 

Baker,  I.  0 123 

Bauschinger,  J 26,  27,  41,  44,  157 

Bergerand  Guillerme 20,44 

Beton  u.  Eisen 61 

Black,  A • 33 

Boston  Transit  Commission. . .  5,  43,  48, 153 

Bouniceau 43 

Brown,  W.  L 147 

Busing  and  Schumann 27,  44,  48 

Canadian  Society  Civil  Engrs. ,  7V<7  ns.  of    60 

Candlot 45 

Carleton,  R.  A.  W 147 

Chief  Engr.  U.  S.  Army;    see  United 
States  Army. 

Christophe 44 

Civil  Ingenieur,  Der 103 

Clark,  T.  F : 34,  129,  155 

Clarke,  E.  C 13,  21,  23,  26,  35,  50,  155 

Coelos,  J.A 147 

Considere 42,  65 

Gostigan,  J.S 60 

Cummings.U 6 

De  Joly 65,  66,  75 

Derleth.W.T 84,  134 

Deutscher  Ingenieure;   see  Zeitsch.  des 

Ver. 
Dougherty,  R.  E 44 


PAGE 

Doyle,  T.  L 131 

Durand-Claye 44,  148,  157 

Dyckerhoff 47 


Engineering  News..  33,  34,  35,  36,  129, 131, 155 
Engineering  Record 37 


Falk,  M.  S 84,  144 

Feret,  R 31,  33,  46,  49,  52,  54,  138 

Fuller,  W.  8 138 


Gary,  M 42 

German  Portland  Cement  Manufac- 
turers'1 society 47 

Gillmore,  Q.  A 16,  105 

Gowen,  C.  S 50,  59 

Grant,  J 13,  25,  26,  41,  126 

Griesenauer,  S.  J 35 

Guillerme 20,  44 

Hallock,  W 45 

Hartig 103 

Hatt,  W.  K 63,  83,  136 

Hawkesworth,  J 84,  134 

Heath 50 

Henby.W.  H 78,  111 

Holman,  M.  L 21 

Hunt,  R.W.,&Co 24 

Institution  of  Civil  Eng.,  Gt.  Brit..  Pro- 
ceedings  13,  25,  26,  41,  49,  53,  126,  147 

Journal  of  Assoc.  Eng.  Societies  ;  see 
Assoc. 

Johnson,  J.  B , 24,  26 

Justice,  E.  R 131 

Lanza,  G 147 

Lamed,  E.  S 32 

Lathbury  &  Spackman,  Inc 5,  13,  25 

LeChatelier 1,  8,  45 

Lesley,  R.  W.  24,  53 


176 


AUTHORS'  INDEX. 


PAGE 

Marburg,  E 119 

McCaustland,  E   J 118,  138,  146 

McCurdy,  H.  S.  R 43 

Meier 44 

Michaelis 45 

Mills,  C    M 37 

Mineral  Industry ^  12 

Morsch,E *  61 

Newberry,  S.  B.  and  W.  B 1,  8 

New  York,  Report  of  State  Engr.  24, 121, 124 
Noble,A.     50 


PAGE 

Technograph,  Univ.  of  Illinois 131 

Testing  Materials;  see  American  So- 
ciety for;  Proceedings. 

Tetmajer 26 

Tornei 42 

Transactions;  see  American  Society  of 
Civil  Eng.;  see  Canadian  Society  of 
Civil  Eng. 


United  States  Army;  Report  Cliief  of 

Engrs 15,  17,  30,  56,  63,  149,  156 

Unwin,  W.  C 26 


Pence,  W.  D 

Fonts  et  Chaussees  ;  see  Annales. 


43 


Rae,  J.G 

Rafter,  Geo.  W. 
Ries&  Eckels.. 


24,  116,  121,  137,  138 
5 


Sherman,  C.  E 36 

Schumann,  C 27,  42,  44,  48 

Spofford,  C 61 

Sussex,  J.  W 130 

Swain,  G.F 40 


Van  Ornum,  J.  L 66 

Von  Schon,  H. 152 


Watertown  Arsenal  Reports  —  3,  4,  10,  14, 

17,  18,  28,  56,  58,   64,   74,   105,   113. 

121,  125,  127,  130,  132,  135,  137,  139 

Western  Society  of  Engrs.,  Proceed,  of,  43,  84 

Wheeler,  E.  S 15,  17,  30,  56,  63,  149,  156 

Whittemore,  D.  T 6 


Zeitschrifl 
nieure  .. 


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